2 Chronicles 18:5
Therefore the king of Israel gathered together of prophets four hundred men, and said unto them, Shall we go to Ramoth-gilead to battle, or shall I forbear? And they said, Go up; for God will deliver it into the king’s hand. Therefore the king of Israel gathered together of prophets four hundred men, and said unto them, Shall we go to Ramoth-gilead to battle, or shall I forbear? And they said, Go up; for God will deliver it into the king’s hand.
Ahab gathered four hundred false prophets to ask whether to go to battle at Ramoth-gilead or to forbear from the campaign. He sought their approval for attacking the city. They urged him to go up, falsely assuring him that God would deliver the city into the king's hand and give him victory. Their answer did not satisfy Jehoshaphat, who then asked for a prophet of the Lord so that God's will might be learned.
Their confident assurance was contradicted by Micaiah's warning that Israel would be left without a king. The kings ignored that warning and went into the battle, where Ahab died, so the true prophetic word was fulfilled rather than the false prediction of success.