Charles Ellicott Commentary Revelation 2:14

"But I have a few things against thee, because thou hast there some that hold the teaching of Balaam, who taught Balak to cast a stumblingblock before the children of Israel, to eat things sacrificed to idols, and to commit fornication." — Revelation 2:14 (ASV)

But I have a few things against you—the word “few” is not to be taken as if the ground of rebuke was a trivial one. The little leaven might leaven the whole lump; and those who had been brave to death in the days of persecution had been less temptation-proof against more seductive influences. The church tolerated without protest men holding [the word is the same as that used in commendation (Revelation 2:13), You hold (fast) My name] the teaching of Balaam, who taught Balak to put a stumbling-block before the sons of Israel; (namely) to eat things sacrificed to idols, and to commit fornication.

Israel could not be cursed, but they might be made to bring a curse upon themselves by yielding to sin; so the counsel of Balaam was to tempt them through the women of Midian, and Behold, these caused the children of Israel to commit trespass against the Lord in the matter of Peor, and there was a plague among the congregation of the Lord (Numbers 31:16). A similar temptation was endangering the Pergamene Church.