Summary: The analysis of Christ's message to Thyatira as set forth in Revelation 2:18-29 teaches us that a church may be working but corrupt.
We are currently in a series of messages titled, “Christ’s Message to the Seven Churches,” that is based on the first three chapters of the Book of Revelation.
In Revelation 1 (quickview)  the resurrected and glorified Christ revealed himself to his Apostle John, and told him to write letters to seven churches in Asia. Today, we shall examine the fourth of those letters, and learn about Christ’s message to his church in Thyatira.
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.’ ” (Revelation 2:18-29 (quickview) )
The Westminster Confession of Faith says the following in Chapter 25, paragraph 5: “The purest churches under heaven are subject both to mixture and error; and some have so degenerated as to become no churches of Christ, but synagogues of Satan. Nevertheless, there shall be always a church on earth to worship God according to his will.” Churches that do not deal with sin in its midst do not practice church discipline, and those churches eventually degenerate “as to become no churches of Christ.”
“If your brother sins against you, go and tell him his fault, between you and him alone. If he listens to you, you have gained your brother. But if he does not listen, take one or two others along with you, that every charge may be established by the evidence of two or three witnesses. If he refuses to listen to them, tell it to the church. And if he refuses to listen even to the church, let him be to you as a Gentile and a tax collector.”