Letters to the Seven Churches

I. Introduction
A. I preached on these seven letters in seven sermons in the summer of 2019 (The Epistles of Jesus – still available on our website), so in this series I am going to cover them all in one sermon.
B. Because the passage is so long, and has so much in it, I have much more than one sermon’s worth today. So, there is more in the notes that I will be able to get to, which I hope you will read later.
C. Revelation 2:1–3:22 “To the angel of the church in Ephesus write: ‘The words of him who holds the seven stars in his right hand, who walks among the seven golden lampstands. 2 “ ‘I know your works, your toil and your patient endurance, and how you cannot bear with those who are evil, but have tested those who call themselves apostles and are not, and found them to be false. 3 I know you are enduring patiently and bearing up for my name’s sake, and you have not grown weary. 4 But I have this against you, that you have abandoned the love you had at first. 5 Remember therefore from where you have fallen; repent, and do the works you did at first. If not, I will come to you and remove your lampstand from its place, unless you repent. 6 Yet this you have: you hate the works of the Nicolaitans, which I also hate. 7 He who has an ear, let him hear what the Spirit says to the churches. To the one who conquers I will grant to eat of the tree of life, which is in the paradise of God.’ 8 “And to the angel of the church in Smyrna write: ‘The words of the first and the last, who died and came to life. 9 “ ‘I know your tribulation and your poverty (but you are rich) and the slander of those who say that they are Jews and are not, but are a synagogue of Satan. 10 Do not fear what you are about to suffer. Behold, the devil is about to throw some of you into prison, that you may be tested, and for ten days you will have tribulation. Be faithful unto death, and I will give you the crown of life. 11 He who has an ear, let him hear what the Spirit says to the churches. The one who conquers will not be hurt by the second death.’ 12 “And to the angel of the church in Pergamum write: ‘The words of him who has the sharp two-edged sword. 13 “ ‘I know where you dwell, where Satan’s throne is. Yet you hold fast my name, and you did not deny my faith even in the days of Antipas my faithful witness, who was killed among you, where Satan dwells. 14 But I have a few things against you: you have some there who hold the teaching of Balaam, who taught Balak to put a stumbling block before the sons of Israel, so that they might eat food sacrificed to idols and practice sexual immorality. 15 So also you have some who hold the teaching of the Nicolaitans. 16 Therefore repent. If not, I will come to you soon and war against them with the sword of my mouth. 17 He who has an ear, let him hear what the Spirit says to the churches. To the one who conquers I will give some of the hidden manna, and I will give him a white stone, with a new name written on the stone that no one knows except the one who receives it.’ 18 “And to the angel of the church in Thyatira write: ‘The words of the Son of God, who has eyes like a flame of fire, and whose feet are like burnished bronze. 19 “ ‘I know your works, your love and faith and service and patient endurance, and that your latter works exceed the first. 20 But I have this against you, that you tolerate that woman Jezebel, who calls herself a prophetess and is teaching and seducing my servants to practice sexual immorality and to eat food sacrificed to idols. 21 I gave her time to repent, but she refuses to repent of her sexual immorality. 22 Behold, I will throw her onto a sickbed, and those who commit adultery with her I will throw into great tribulation, unless they repent of her works, 23 and I will strike her children dead. And all the churches will know that I am he who searches mind and heart, and I will give to each of you according to your works. 24 But to the rest of you in Thyatira, who do not hold this teaching, who have not learned what some call the deep things of Satan, to you I say, I do not lay on you any other burden. 25 Only hold fast what you have until I come. 26 The one who conquers and who keeps my works until the end, to him I will give authority over the nations, 27 and he will rule them with a rod of iron, as when earthen pots are broken in pieces, even as I myself have received authority from my Father. 28 And I will give him the morning star. 29 He who has an ear, let him hear what the Spirit says to the churches.’
D. 3:1 “And to the angel of the church in Sardis write: ‘The words of him who has the seven spirits of God and the seven stars. “ ‘I know your works. You have the reputation of being alive, but you are dead. 2 Wake up, and strengthen what remains and is about to die, for I have not found your works complete in the sight of my God. 3 Remember, then, what you received and heard. Keep it, and repent. If you will not wake up, I will come like a thief, and you will not know at what hour I will come against you. 4 Yet you have still a few names in Sardis, people who have not soiled their garments, and they will walk with me in white, for they are worthy. 5 The one who conquers will be clothed thus in white garments, and I will never blot his name out of the book of life. I will confess his name before my Father and before his angels. 6 He who has an ear, let him hear what the Spirit says to the churches.’ 7 “And to the angel of the church in Philadelphia write: ‘The words of the holy one, the true one, who has the key of David, who opens and no one will shut, who shuts and no one opens. 8 “ ‘I know your works. Behold, I have set before you an open door, which no one is able to shut. I know that you have but little power, and yet you have kept my word and have not denied my name. 9 Behold, I will make those of the synagogue of Satan who say that they are Jews and are not, but lie—behold, I will make them come and bow down before your feet, and they will learn that I have loved you. 10 Because you have kept my word about patient endurance, I will keep you from the hour of trial that is coming on the whole world, to try those who dwell on the earth. 11 I am coming soon. Hold fast what you have, so that no one may seize your crown. 12 The one who conquers, I will make him a pillar in the temple of my God. Never shall he go out of it, and I will write on him the name of my God, and the name of the city of my God, the new Jerusalem, which comes down from my God out of heaven, and my own new name. 13 He who has an ear, let him hear what the Spirit says to the churches.’ 14 “And to the angel of the church in Laodicea write: ‘The words of the Amen, the faithful and true witness, the beginning of God’s creation. 15 “ ‘I know your works: you are neither cold nor hot. Would that you were either cold or hot! 16 So, because you are lukewarm, and neither hot nor cold, I will spit you out of my mouth. 17 For you say, I am rich, I have prospered, and I need nothing, not realizing that you are wretched, pitiable, poor, blind, and naked. 18 I counsel you to buy from me gold refined by fire, so that you may be rich, and white garments so that you may clothe yourself and the shame of your nakedness may not be seen, and salve to anoint your eyes, so that you may see. 19 Those whom I love, I reprove and discipline, so be zealous and repent. 20 Behold, I stand at the door and knock. If anyone hears my voice and opens the door, I will come in to him and eat with him, and he with me. 21 The one who conquers, I will grant him to sit with me on my throne, as I also conquered and sat down with my Father on his throne. 22 He who has an ear, let him hear what the Spirit says to the churches.’ ”
II. Observations from chart
A. Names of Jesus are all derived from chapter one, except Rev.3:7-9, “The words of the holy one, the true one, who has the key of David, who opens and no one will shut, who shuts and no one opens.” There’s an addendum at the end of the notes to read later which addresses this twist at length.
B. “I know” is the first part of the special message in each letter.
1. Jesus knows. And He wants us to remember that He knows. He reminds us 7 times!
2. He doesn’t just know individuals; He knows churches. He knows what they’re going through, what they’re dealing with.
3. And He doesn’t just see on the outside like we do, He sees into the heart: “You have the reputation of being alive, but you are dead,” He says to Sardis in Rev.3:1.
4. And not only does He know churches —– but He has something to say to churches.
C. The seven letters begin very similarly, and they end very similarly. But the heart of the message Jesus has for each church is very different. In this we see that the seven churches are in very different situations. Some are in pretty good shape; others are dangling over the cliff. Two are told that if they don’t repent, their lampstand will be removed. Two are commended without any rebuke whatsoever. And four are mixed, commended for some things and rebuked for others.
1. And so Jesus deals with them in different ways. He’s not a cookie-cutter God who just runs everyone through the same process. He has a custom-designed curriculum and training process for each person and each church.
2. But there’s another way the letters are similar to one another. When the church is corrected by Jesus for some failing, His solution is always the same: repent. It is mentioned 8 times in these 7 letters. Every time Jesus corrects one of His churches, He follows that by calling them to repent.
3. Sin is not just moral; it is relational. You can try to reform by yourself, but repenting goes to God.
D. The one who conquers: a vivid series of synonyms for heaven/eternal life/final reward.
E. He who has an ear: If you have been given the ability to grasp these things, don’t let it go to waste. Most people don’t have that ability. You’ve been given a treasure. Don’t hide it in a closet.
1. So many times when Christians are struggling with anger or fear or lust or something else, it is because they have eyes to see but they’re just not looking. Somewhere in the Bible, God has spoken about the thing you’re struggling with. So, find what He’s said and listen to it!
III. So, what are the applications to our lives which we can make from the seven letters as a whole?
A. First, it is a great reminder of where we are today and where we’ll be tomorrow.
1. The church in this age is different than the church in the age to come.
2. We have seen from reading Acts, Galatians and Corinthians that the churches in the middle of the first century certainly had their problems.
3. But now in these seven churches we can see that the pattern continued through the end of century.
a. The church of Ephesus had abandoned the love for Christ which they had at first (Rev.2:4).
b. Pergamum & Thyatira were putting up with false teaching, including teaching which encouraged sexual immorality (Rev.2:14-15; 2:20).
c. Sardis had a reputation of being alive, but inside they were dead (Rev.3:1).
d. Laodicea was lukewarm and made Jesus feel like vomiting (Rev.3:15-16).
e. Ephesus & Sardis were in such bad shape that Jesus threatens that if they don’t repent soon, He is going to come against them (Rev.2:5; 3:3).
f. And it’s pretty clear that the worst churches had no idea they were so bad off. This is nowhere clearer than in the letter to Laodicea: “You say, I am rich, I have prospered, and I need nothing, not realizing that you are wretched, pitiable, poor, blind, and naked.” (Rev.3:17)
4. This is the way things have been down through the ages of the church. And today is no different.
5. The church is a mixed bag. This is who we are. We are sinners and therefore the church is wracked with problems and weaknesses. And it’s been that way since the first century.
6. We don’t just know that by experience; we know it from the Bible. The people who say that we should go back to the way things were in the NT apparently haven’t read the NT.
7. But here’s the beautiful thing about the book of Revelation: it starts with the church of now, the church of this age, in all its messiness, BUT IT DOESN’T END THERE.
8. It ends with the church AS IT WILL BE WHEN CHRIST RETURNS and cleans up all the mess.
9. Revelation 21:9 One of the seven angels said, “Come, I will show you the Bride, the wife of the Lamb.” 10 And he carried me away in the Spirit to a great, high mountain, and showed me the holy city Jerusalem coming down out of heaven from God, 11 having the glory of God, its radiance like a most rare jewel, like a jasper, clear as crystal...22 I saw no temple in the city, for its temple is the Lord God the Almighty and the Lamb. 23 The city has no need of sun or moon to shine on it, for the glory of God gives it light, and its lamp is the Lamb...and there will be no night there. 24 the kings of the earth will bring...into it the glory and the honor of the nations. 27 But nothing unclean will ever enter it, nor anyone who does what is detestable or false, but only those who are written in the Lamb’s book of life.
10. So we see the beginning and the end of Revelation like two bookends.
a. Rev.2-3 are the church as it is in the present; Rev.21 is the church as it will be on the last day.
b. Rev.2-3 are where we are. Rev.21 is where we are going.
11. We believe in the church for two reasons:
a. It has a glorious future. That’s why we invest in it: one day its stock is going to soar to unimaginable heights! The church will not always be where it is now. In spite of its present troubles and failures, the church has a glorious destiny. One day it will be united, spotless, glorious, sinless and beautiful beyond imagination. That’s where this train is going. And that’s why I’m not getting off the train.
b. The second one is our next point...
B. We see in these letters that Jesus is invested in His churches.
1. Think about the significance of these words of Jesus in these epistles. Jesus comes to earth and spends three years training twelve disciples. Then He dies on the cross and is raised on the 3rd day. After 40 days He ascends to heaven, and ten days later pours out His Spirit at Pentecost. And now, over 60 years later, Jesus is dictating these letters to the seven churches of Asia.
2. During those 60+ years, the apostles labored by the power of the HS to plant churches all over the Roman world, to make foundational decisions, and to write the NT. All through this time Jesus is still speaking, but mostly through His apostles. But gradually the apostles die off. But then right before the last apostle dies, right before the capstone of the NT is put in place, Jesus speaks directly/personally one final time to seven churches in Asia Minor.
3. It had now been over 40 years since Paul brought the gospel to this part of Asia Minor. There are now multiple churches in the area. After Paul’s second letter to Timothy, the NT gives us no information about how the churches were doing for the next 30 years or so. But now these seven letters are the last indication we have about what kinds of things the church was dealing with at the end of the 1st century.
4. A lot has happened in the years since He walked on earth, especially to the Jewish people.
a. The Judaizer controversy troubles the church and requires the Council of Jerusalem.
b. All the apostles have died, martyred for their testimony about Christ. Many Christians die as well.
c. The whole NT is written, with the exception of this book of Revelation.
d. The city of Jerusalem has been ruined and many Jews have been massacred by the Romans.
5. Remember Moses sheperding his sheep in Midian when God appeared to him? Moses was worried about finding pasture and keeping safe and stayinig hydrated. What was God concerned about? “I have heard the cries of my people in Egypt.” (Exodus 3:7)
6. Remember when Jesus was walking through the town square in Jericho, surrounded by a massive crowd eager to catch a glimpse? What was Jesus concerned about? Blind Bartimaeus on the edge of the crowd calling out desperately to the Son of David (Mark 10:46-52).
7. And now in a world rife with diseases, wars, injustices, poverty, what is Jesus concerned about?
a. He’s concerned about the fading first love of the believers in Ephesus. He’s worried about how the believers in Smyrna are going to react to the brutal, upcoming persecution. He’s concerned about the false teaching which is being tolerated in Pergamum. He’s concerned about the bad influence which a certain woman is having on many in Thyatira. He’s concerned about the lukewarm faith of the Laodiceans.
8. And of all the wonderful things happening in the world: great pieces of art being produced, great discoveries begin made, great love stories taking place, great advances in knowledge and science, what was Jesus excited about? He’s excited about:
a. The patient endurance in the church at Ephesus in the face of brutal persecution.
b. The willingness of the church at Smyrna to suffer poverty, knowing they are rich in Christ.
c. He’s excited about the church in Pergamum holding fast to His name even though one of their most important members has recently been martyred for his faithful testimony.
d. The church in Philadelphia keeping His word even though in that society they had been stripped of any power – on account of their faith in Christ.
9. Do you see how close to the heart of Jesus is the welfare of His local churches?
10. This isn’t surprising. It’s His church; He loves it and He’s building it. So, it’s where His heart is: How are My churches doing? What are My churches believing? Who are they listening to? How are they living? What are they focused on? Are they being the light of the world?
11. Jesus isn’t just concerned about individual Christians. We see here that He is also interested in and working on churches. He said He’d build His church and the gates of hell would not prevail.
12. Churches are not just earthly institutions which some people find helpful to their faith. They belong to Jesus, and He is personally involved with them. Jesus doesn’t just have a personal relationship with each of His people; He has a relationship with each of His churches. And He’s communicating with them, affirming them, correcting them, assisting them.
13. We saw that it seems to say that each church has a guardian angel in Rev.1:20. I believe churches are known and talked about in the heavenly places.
14. And if heaven cares about them, and if Jesus cares about them, we should care about them too.
15. Whatever church a believer is a part of, that church influences them and also influences others. The healthier the church is, the better off we all are. So everyone should have a zeal for the wellness of the Lord’s churches.
16. How can a person love Jesus but not love His church?
17. And today, when so many are giving up on the church, there is no better justification for doing so than in the first century.
C. Even though Christian churches have many flaws, we must remember that it’s not all bad.
1. There were a lot of good things happening in the 7 churches, which Christ commended them for.
2. And there are good things happening today. And good things will happen in the future.
3. So, as we wait for the Lord’s return, we work with what we’ve got, knowing that the Lord is more invested than we’ll ever be.
4. Because of Him, even in this age, churches are capable of terrific things.
5. The hardest thing about pastoring is seeing how your own sin damages Christ’s people & church.
6. But one of the greatest things about pastor is seeing the Lord do many beautiful things in people’s lives, and being associated with so many heroes of the faith.
a. People who cling to Christ even in the face of unspeakable tragedy.
b. People saying yes to Christ even though it means saying no to earthly hopes and dreams.
c. People who obey Christ’s commands even when it feels like it’s going to kill them.
7. Can I give a few examples?
a. Racism/slavery – In the first hundred years of slavery in America, very few black slaves embraced the Christian faith of their captors and masters, who tried to use Scripture to justify their racist oppression. It is human nature to resist the ideology of your oppressors. But the Great Awakening changed all that, beginning in the late 1730's, when preachers began to preach a gospel of love for all men, even slaves, and black people fell in love with the real Christ, not with the white man’s Christ. It seems to me amazing and miraculous that today, after all that happened to African-Americans in slavery and in the years afterward, there are a higher percentage of African-Americans in America who claim the name of Christ than there are white people.
b. SSA – There are many Christians who experience same sex attraction, even though it’s the last thing they want to experience. And in a day when there is so much pressure to follow your heart and so much ammunition to rationalize doing so, it’s amazing that so many recognize God’s will in Scripture & say no to their desires. It’s another beautiful & powerful testimony of God’s grace.
c. Abuse – Over the last 21 years, there has been a lot in the news about abuse in the church. And this gives us a glimpse of the worst and the best of Christ’s church. The worst, of course, is those who shame Christ by using His name and His church to exploit and destroy for their own pleasures, or who protect those who do. But the best is also seen in this, that so many of the abused have not turned away from Christ – or even from His church – in spite of their experience.
8. The world is not worthy of people like this! (Heb.11:38) And this kind of stuff doesn’t happen by itself. God is the One who does this.
9. It’s a great privilege to know and worship together with those for whom to live is Christ.
D. The mixed report Jesus gives to the seven churches is also instructive in another way. It shows us that Jesus gives both affirmation and rebuke. This might be obvious, but for many, it seems, it’s not.
1. In every generation there are favorite ways to portray Jesus. But what protects us from having a skewed perception of who He really is? Looking back at who He actually is in the NT.
2. There have been times in church history when the thrust was negative, which bludgeons the people with rebukes and plays on people’s guilt. This is how it was with the Pharisees who pile up heavy burdens on people and then do nothing to help them lift it (Matt.23:4). And unfortunately you can still find churches like that today. And it’s harmful.
3. But in our present context, it seems to me, there are more churches promoting a Christianity which is exclusively positive, and avoids all rebukes, all criticisms, all warnings. Some preachers take what’s written about those who are seeking Him first and apply it even to those who are trying to serve two masters, or whose faith is lukewarm.
4. But these letters show us that Jesus is not always pleased; He often has things against His people.
a. Only two of the seven churches escaped without correction.
b. Listen to Rev.3:2-3: “Wake up, and strengthen what remains and is about to die, for I have not found your works complete in the sight of my God. Remember, then, what you received and heard. Keep it, and repent. If you will not wake up, I will come like a thief, and you will not know at what hour I will come against you.”
c. There are many churches in today’s America where you’ll never heard words like that. People might leave the church if you talk like that!
E. The Lord’s primary tool for the renewal and reformation of His churches is His word.
1. John’s vision Revelation 1 has Jesus walking in the midst of seven lampstands – representing these seven churches – just like the priest cared for and maintained the lampstand in the temple.
2. And in these seven letters we see Jesus using the sword which came out of His mouth to do this work. We see that the lampstands are definitely in need of the Priest’s attention and repair.
a. There is a new temple now – it is made up of living stones – God’s people.
b. And the One who cleansed the old temple is also cleaning the new, as we see in Rev.2-3.
c. This is why the word of God must have such a central role in the life of the church.
d. It’s is Christ’s tool to do His work!
3. You know, to many people preaching, reading the Bible, singing Scripture songs, going to Sunday school and Bible studies seems awfully boring. It’s always the same thing: Bible/Bible/Bible.
a. Church life might seem boring – until you realize that Jesus is among His churches using His word to keep them glowing and shining and lighting the dark world.
b. Invisible to many, a very important and powerful thing is happening: Christ is at work, communicating His love, assuring, convicting, instructing.
4. The reason churches need to be bible-centered is because churches need encouragement from Jesus; they need exhortation & correction from Jesus.

Addendum: Thoughts on Rev.3:7-10

In introducing Himself as the author of each of His seven letters to the seven churches in Rev.2-3, Jesus uses language derived from Rev.1:

2:1 “The words of him who holds the seven stars in his right hand, who walks among the seven golden lampstands” from Rev.1:16 and Rev.1:12-13.
2:8 “The words of the first and the last, who died and came to life” from Rev.1:8.
2:12 “The words of him who has the sharp two-edged sword” from Rev.1:16.
2:18 “The words of the Son of God, who has eyes like a flame of fire, and whose feet are like burnished bronze” from Rev.1: 14-15.
3:1 “The words of him who has the seven spirits of God and the seven stars.” from Rev.1:4 and 16.

Then, all of a sudden, the pattern changes. Jesus introduces Himself in the letter to the church in Philadelphia this way in Rev.3:7, “The words of the holy one, the true one, who has the key of David, who opens and no one will shut, who shuts and no one opens.” Nowhere in chapter one is Jesus said to have the key of David. The only reference to Him having a key in chapter one is in v.18, which says He has the keys of Death and Hades. And nowhere does it say that Jesus is the One “who opens and no one will shut, who shuts and no one opens.” All this comes from Isaiah 22:22, which says, “I will place on his shoulder the key of the house of David. He shall open, and none shall shut; and he shall shut, and none shall open.” This is found in Isaiah 22 in the context of God saying to Shebna (steward of King Hezekiah) that a man named Eliakim, will replace him as manager of King Hezekiah’s household: “In that day I will call my servant Eliakim the son of Hilkiah (the priest), and I will clothe him with your robe, and will bind your sash on him, and will commit your authority to his hand. And he shall be a father to the inhabitants of Jerusalem and to the house of Judah. 22 And I will place on his shoulder the key of the house of David. He shall open, and none shall shut; and he shall shut, and none shall open.” (Isaiah 22:20–22)

Now why would Jesus cite this passage about Eliakim to introduce Himself to the Philadelphians? Why didn’t He just introduce Himself simply as the One who has the keys of death and of Hades (1:18)? Why instead does He change it to “the One who has key of David, who opens and no one will shut, who shuts and no one opens.” And then why does He add, “Behold, I have set before you an open door, which no one is able to shut.”?

It seems that Jesus is turning the key/door image to fit the situation the church of Philadelphia found themselves in. But before we get to that, let me lay out some Bible background about the opening of doors. When Jesus calls Himself the Key of David, and the One who shall open and none shall shut, when Jesus says to the believers in Philadelphia that He has “set before [them] an open door, which no one is able to shut,” we can only understand what He means if we understand that this is gospel imagery, salvation imagery. You see, when Adam and Eve sinned in the garden of Eden, God cast them out of the garden and placed an angel at the entrance with a flaming sword to prevent them from coming back in. The way into God’s presence was closed. And for centuries, this separation remained in place. Then, when Moses was given instructions for building the tabernacle, it included directions for making a curtain or veil (Ex. 26:30–35). This veil was to be embroidered with cherubim, representing the cherubim of Eden, keeping mankind away from the presence of God. But then, astonishingly, at the moment Jesus died on the cross, the temple curtain was torn from top to bottom (Matt.27:50-51), symbolizing God finally opening the door. Why at that moment? Because at that moment the door was opened by means of the atoning death of Christ. This is why Jesus said “I am the door.” (John 10:9) This is why Hebrews 10:19-22 says, “Brothers, since we have confidence to enter the holy places by the blood of Jesus, by the new and living way that he opened for us through the curtain, that is, through his flesh, and since we have a great priest over the house of God, let us draw near with a true heart in full assurance of faith.”

That brings us to Christ’s reference to the door in Rev.1:18 and 3:7-8. The believers in the church of Philadelphia are experiencing something which explains perfectly everything Jesus says: like the believers at Smyrna, they are suffering persecution. We get a hint of this in v.8, where He commends them for their behavior in persecution: “I know that you have but little power, and yet you have kept my word and have not denied my name.” In v.9 their persecutors are referred to as “those of the synagogue of Satan who say that they are Jews and are not, but lie.” This situation is similar to the one in Smyrna, about which Jesus says, “I know...the slander of those who say that they are Jews and are not, but are a synagogue of Satan” (Revelation 2:9). The synagogues in these cities were filled with Jews who rejected Jesus as their messiah and set themselves against the gospel of Christ, and against the people of Christ. So, how were the unbelieving Jews persecuting them? We’re not told specifically here, but I don’t think it’s too hard to figure out from the pattern in the rest of the NT. One of the main tools of persecution which the Jews used against those who had become Christians was excommunication: they kicked them out of the synagogue.
a. John 9:22 “The Jews had already agreed that if anyone should confess Jesus to be Christ, he was to be put out of the synagogue.”
b. John 12:42 “Many even of the authorities believed in [Jesus], but for fear of the Pharisees they did not confess it, so that they would not be put out of the synagogue.”
c. John 16:2 “They will put you out of the synagogues.”
The membership of the synagogue was supposed to represent being a part of God’s people, being one of God’s children. And being put out was supposed to represent being cut off from God. If we suppose that the unbelieving Jews of Philadelphia have rejected/excommunicated the Christians from the synagogue, then Jesus’ response about opening a door makes perfect sense. To put it plainly, what is Jesus going to do about this exclusion from the synagogue? How is Jesus going to respond when His people have been cast out and the door slammed behind them? He will set before them “an open door which no one is able to shut.” Jesus says, “They may have slammed the door in your face, but I am throwing open the door to you! And no one will be able to close it!” And then He says more: “Behold, I will make them come and bow down before your feet, and they will learn that I have loved you.” Jesus assures them that not only will He keep the door open for them, but He will personally make sure that in the end their excommunicators will bow down to them and acknowledge that they are not rejected by God but greatly loved by God.

What a marvelous promise Jesus gives to His people! Not only will they know that they are the ones the Lord loves, but even those who spent their lives telling them they were what was wrong with the world will know not only that they were right about God, but that they are His beloved people. “The sons of those who afflicted you shall come bending low to you, and all who despised you shall bow down at your feet; they shall call you the City of the LORD, the Zion of the Holy One of Israel.” – Isaiah 60:14

But why Isaiah 22? Did Jesus just randomly pick some Old Testament passage because it talked about somebody opening a door that no one could close?

To help answer this question, here is a section of G.K Beale’s comments on the use of Isaiah 22:22 in Rev.1:7:

Isa. 22:22 is not merely applied analogically in Rev.3:7 but is understood as an indirect typological prophecy conveyed through Isaiah’s historical narration, not as a direct verbal, messianic prophecy. This is indicated by five observations.
1. First, whenever David is mentioned in connection with Christ in the NT there are usually discernible prophetic, messianic overtones (e.g., Matt. 1:1; 22:42–45; Mark 11:10; 12:35–37; Luke 1:32; 20:41–44; John 7:42; Acts 2:30–36; 13:34; 15:16; Rom. 1:1–4; 2 Tim. 2:8). The only other occurrences of “house of David” in the NT have the same prophetic nuance (Luke 1:27, 69; so also “tabernacle of David” in Acts 15:16), as do the only remaining references to David in Revelation, both of which are allusions to messianic prophecies of Isaiah (Rev. 5:5; 22:16 [cf. Isa. 11:1, 10]).
2. Second, the reference to Eliakim (the son of Hilkiah the priest, and the manager of King Hezekiah’s household - ed.) as “my servant” in Isa. 22:20 would have been easily associated with the servant prophecies in Isaiah 40–53, since the phrase occurs there thirteen times (and only twice elsewhere in Isaiah, in reference to the prophet himself [20:3] and to David [37:35]).
3. Third, the placing of “the key of the house of David,” that is, administrative responsibility for the kingdom of Judah, “on his [Eliakim’s] shoulder,” the allusion to him as a “father” to those in “Jerusalem and the house of Judah,” and the reference to his “becoming a throne of glory” would all have facilitated such a prophetic understanding of Isa. 22:22, since this language is so strikingly parallel to the prophecy in Isa. 9:6–7 of the future Israelite ruler (“… the government will be on his shoulders … and his name will be called … eternal father,” who sits “on the throne of David”).
4. Fourth, that Isa. 22:22 is viewed in a prophetic, typological manner is further evident from the intentional allusions to prophetic “servant” passages (Isa. 43:4; 45:14; 49:23) in Rev. 3:9. But there the allusions are applied to the church, though the rationale for the application lies in an understanding of the church’s corporate identification with Jesus as God’s servant and true Israel (e.g., Isa. 49:3–6 and the use of 49:6 in Luke 2:32; Acts 13:47; 26:23; note how Christ and the church fulfill what is prophesied of Israel in the OT).
5. Fifth, the main typological correspondence between Eliakim and Christ is that Christ, like Eliakim, was to have absolute power over the Davidic throne as king. Whereas Eliakim’s control was primarily political, Christ’s was to be primarily spiritual, as well as ultimately universal in all aspects; whereas Eliakim was to rule over Jerusalem, Judah, and the house of David, Christ’s sovereignty was to extend over all peoples.

The context of Isa. 22:22 reveals other correspondences between Eliakim and Christ; even though it is difficult to know whether John had all of them in mind, together they show why it was so attractive to apply this OT passage to Christ: (1) As Eliakim was specially appointed to his royal office by Yahweh (Isa. 22:20-21 - ed.), so Christ was appointed to a greater royal office by God. (2) As Eliakim’s office may have included some sort of priestly concerns, such concerns were made a primary concern with Christ’s royal office. An early Jewish understanding of the priestly nature of Eliakim’s office is testified to by the paraphrase of Isa. 22:22 in the Targum, a paraphrase which, as we have seen, gives control of “the sanctuary” to Eliakim. Midr. Rab. Exod. 37.1 understands Eliakim in Isa. 22:23 as a “high priest.” And it is no coincidence that in Rev. 3:12 Christ also is seen as having power over who enters God’s temple (note also the probable priestly description of Christ in 1:13). (3) As Eliakim’s power was equal to the king’s, so would Christ’s be equal to God’s. — Beale, G. K. (1999). The book of Revelation: a commentary on the Greek text (pp. 284–285). (Slightly rephrased for understandability)