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 shall deliver it into the hand of the king.
The king of Israel gathered about four hundred prophets and asked them whether to go to battle against Ramoth-gilead or to hold back, and they answered together that he should go up because the Lord would deliver it into the hand of the king. Those four hundred were false prophets, and their confident assurance of victory from God was false. Their favorable answer was not received as sufficient authority, for Jehoshaphat sought a prophet of the Lord beyond that group.
Their counsel stands in contrast to Micaiah's true warning that Israel would be scattered and return to their homes. The kings refused to heed that warning and proceeded with the attack. Ahab died in the battle, fulfilling the prophet's word.