Revelation 3:14

We now come to the last and worst of all the seven Asian churches, the reverse of the church of Philadelphia; for, as there was nothing reproved in that, here is nothing commended in this, and yet this was one of the seven golden candlesticks, for a corrupt church may still be a church. Here we have, as before, I. The inscription, to whom, and from whom. 1. To whom: To the angel of the church of Laodicea. This was a once famous city near the river Lycus, had a wall of vast compass, and three marble theatres, and, like Rome, was built on seven hills. It seems, the apostle Paul was very instrumental in planting the gospel in this city, from which he wrote a letter, as he mentions in the epistle to the Colossians, the last chapter, in which he sends salutations to them, Laodicea not being above twenty miles distant from Colosse. In this city was held a council in the fourth century, but it has been long since demolished, and lies in its ruins to this day, an awful monument of the wrath of the Lamb. 2. From whom this message was sent. Here our Lord Jesus styles himself the Amen, the faithful and true witness, the beginning of the creation of God. (1.) The Amen, one that is steady and unchangeable in all his purposes and promises, which are all yea, and all amen. (2.

— Matthew Henry's Concise Commentary (public domain)

Laodiceans--The city was in the southwest of Phrygia, on the river Lycus, not far from Colosse, and lying between it and Philadelphia. It was destroyed by an earthquake, A.D. 62, and rebuilt by its wealthy citizens without the help of the state [TACITUS, Annals, 14.27]. This wealth (arising from the excellence of its wools) led to a self-satisfied, lukewarm state in spiritual things, as Rev 3:17 describes. See on Col 4:16, on the Epistle which is thought to have been written to the Laodicean Church by Paul. The Church in latter times was apparently flourishing; for one of the councils at which the canon of Scripture was determined was held in Laodicea in A.D. 361. Hardly a Christian is now to be found on or near its site. the Amen-- (Isa 65:16, Hebrew, "Bless Himself in the God of Amen . . . swear by the God of Amen," Co2 1:20). He who not only says, but is, the Truth. The saints used Amen at the end of prayer, or in assenting to the word of God; but none, save the Son of God, ever said, "Amen, I say unto you," for it is the language peculiar to God, who avers by Himself. The New Testament formula, "Amen. I say unto you," is equivalent to the Old Testament formula, "as I live, saith Jehovah." In John's Gospel alone He uses (in the Greek) the double "Amen," Joh 1:51; Joh 3:3, &c.; in English Version," Verily, verily.

— Jamieson-Fausset-Brown Commentary (public domain)