2 Chronicles 18:29

29The king of Israel said to Jehoshaphat, “18:29 Jehoshaphat may have agreed to this because he thought it was a noble gesture on Ahab’s part; i.e. Ahab fighting incognito alongside his troops while Jehoshaphat would presumably stay aloof under the protection of his own bodyguard. More likely Ahab’s plan was simply to disguise himself and let Jehoshaphat be the target by unwittingly serving as Ahab’s double, and the plan very nearly succeeded.I will disguise myself and will go into battle, but you put on your [royal] robes.” So the king of Israel disguised himself, and they went into the battle.