I will disguise myself - Ahab had probably heard of Ben-hadad’s order to his captains 1 Kings 22:31.
Related Commentaries of 1 Kings 22:30
1 Kings 22:30
30 And the king of Israel said unto Jehoshaphat, I will disguise myself, and enter into the battle; but put thou on thy robes. And the king of Israel disguised himself, and went into the battle.