Wolf in Sheep's Clothing

Numbers 22-25 introduces the prophet Balaam, who appears at first glance to be a godly man. He tells the people that Balak has sent to him that he can only say what God says, and that he cannot be bought in order to do otherwise. When he meets Balak he blesses Israel four times, which was exactly the opposite of what Balak wanted him to do. But Balaam is not done, and Israel is seduced by the women of Moab, Balak's people, as well as the women of Midian.

False prophets are not always easy to spot, but they, like trees, are known by their fruit.  Balaam's desire to get paid by Balak caused him to look for other ways to afflict Israel, which showed that he was rebellious at heart, despite his ability to get revelation from God.