1 Kings 20:40

And as the king passed by, he cried unto the king: and he said, Thy servant went out into the midst of the battle; and, behold, a man turned aside, and brought a man unto me, and said, Keep this man: if by any means he be missing, then shall thy life be for his life, or else thou shalt pay a talent of silver.

And he hasted, and took the ashes away from his face; and the king of Israel discerned him that he was of the prophets.