Charles Ellicott Commentary 1 Kings 22:6

"Then the king of Israel gathered the prophets together, about four hundred men, and said unto them, Shall I go against Ramoth-gilead to battle, or shall I forbear? And they said, Go up; for the Lord will deliver it into the hand of the king." — 1 Kings 22:6 (ASV)

Prophets ... four hundred. —These were clearly not avowed prophets of Baal, or the Asherah (“groves”), as is obvious from the context and from their words in 1 Kings 22:12. But Jehoshaphat’s discontent makes it equally clear that they were not in his view true prophets of Jehovah. Probably they were devoted, like the old prophet of Bethel, to the service of the idolatry of Jeroboam.