Revelation 2:14
“But I have a few things against thee, because thou hast there them that hold the doctrine of Balaam, who taught Balac to cast a stumblingblock before the children of Israel, to eat things sacrificed unto idols, and to commit fornication.”
And to the angel of the church in Pergamos write; These things saith he which hath the sharp sword with two edges;
I know thy works, and where thou dwellest, even where Satan’s seat is: and thou holdest fast my name, and hast not denied my faith, even in those days wherein Antipas was my faithful martyr, who was slain among you, where Satan dwelleth.
But I have a few things against thee, because thou hast there them that hold the doctrine of Balaam, who taught Balac to cast a stumblingblock before the children of Israel, to eat things sacrificed unto idols, and to commit fornication.
So hast thou also them that hold the doctrine of the Nicolaitans, which thing I hate.
Repent; or else I will come unto thee quickly, and will fight against them with the sword of my mouth.
Counter-Arguments
The strongest case that this verse does not belong in this theme.

Cross-References
“Notwithstanding I have a few things against thee, because thou sufferest that woman Jezebel, which calleth herself a prophetess, to teach and to seduce my servants to commit fornication, and to eat things sacrificed unto idols.”
“Woe unto them! for they have gone in the way of Cain, and ran greedily after the error of Balaam for reward, and perished in the gainsaying of Core.”
“Nevertheless I have somewhat against thee, because thou hast left thy first love.”
“Behold, these caused the children of Israel, through the counsel of Balaam, to commit trespass against the Lord in the matter of Peor, and there was a plague among the congregation of the Lord.”
“Which have forsaken the right way, and are gone astray, following the way of Balaam the son of Bosor, who loved the wages of unrighteousness;”