Revelation 2:14-15

But I have a few things against you, because you have there some [among you] who are holding to the [corrupt] teaching of Balaam, who taught Balak to put a stumbling block before the sons of Israel, [enticing them] to eat things that had been sacrificed to idols and to commit [acts of sexual] immorality. [Num 25:1, 2; 31:16] You also have some who in the same way are holding to the teaching of the Nicolaitans.