2 Peter 2:16

but was rebuked for his iniquity; the dumb ass, speaking with man's voice, forbade the madness of the prophet.

The character and the motive of the false teachers is brought out strongly by the comparison with the behavior of Balaam: Having left the right way, they have gone astray, by exactly following the way of Balaam, the son of Bosor, who loved the wages of unrighteousness, but received a rebuke for his transgression; the dumb ass, speaking with the voice of a man, hindered the prophet's senseless behavior. The manner in which most false teachers go wrong is exemplified by Balaam, Numbers 22:5; Numbers 23:1; Numbers 24:1. Although the Lord had expressly told him that he must not curse the children of Israel, yet the bribe money which was offered by Balak, king of the Moabites, induced him to make an attempt at cursing Israel. His greed for money was stronger than his obedience to God. He was conscious that he was tempting God in setting out on his mission, and an evil conscience made him irritable. When his ass tried to crowd out of the way at the appearance of the angel, he beat her unmercifully, until the Lord Himself opened her mouth and rebuked Balaam for his transgression, for his foolish, senseless behavior, for his madness. Thus it is madness that has taken hold of the false teachers when they put aside all virtue and become adepts in every form of unrighteousness, at the same time drawing with them the souls of men.