2 Chronicles 18:3, 29-32

And Ahab king of Israel said unto Jehoshaphat king of Judah, Wilt thou go with me to Ramoth-gilead? And he answered him, I am as thou art, and my people as thy people; and we will be with thee in the war.

And the king of Israel said unto Jehoshaphat, I will disguise myself, and will go to the battle; but put thou on thy robes. So the king of Israel disguised himself; and they went to the battle. Now the king of Syria had commanded the captains of the chariots that were with him, saying, Fight ye not with small or great, save only with the king of Israel. And it came to pass, when the captains of the chariots saw Jehoshaphat, that they said, It is the king of Israel. Therefore they compassed about him to fight: but Jehoshaphat cried out, and the LORD helped him; and God moved them to depart from him. For it came to pass, that, when the captains of the chariots perceived that it was not the king of Israel, they turned back again from pursuing him.