2 Peter 2:15-16

15 forsaking the right way, they have gone astray, having followed the way of Balaam, the son of Beor, who loved the wages of unrighteousness; 16 but he received a rebuke for his own transgression, for a mute donkey, speaking with a voice of a man, restrained the madness of the prophet.

The false prophets of Peter’s day were following the way of Balaam, an Old Testament prophet who pretended to be a true prophet of God, but who practiced magic and divination for hire. He was known for traveling on his donkey to curse Israel for the king of Moab (for a price), but he was prevented from it by angels and his donkey that spoke to him (Nu. 22-24).