He was of the prophets - Josephus and others conjecture that this prophet was Micaiah, the son of Imlah (but compare 1 Kings 20:13 note).

Took the ashes away - He took the bandage from off his eyes: see on 1 Kings 20:38 (note). It was no doubt of thin cloth, through which he could see, while it served for a sufficient disguise.

And he hasted, and took away the ashes from his face,.... Took off the linen cloth from his eyes, unveiled or unmasked himself:

and the king of Israel discerned him, that he was of the prophets; he knew him again, having seen him once or twice before; otherwise there could be nothing in his face that could discover him to be a prophet, rather he was to be known by his habit.

Then the disciple of the prophets drew the bandage quickly from his eyes, so that the king recognised him as a prophet, and announced to him the word of the Lord: "Because thou hast let go out of thy hand the man of my ban (i.e., Benhadad, who has fallen under my ban), thy life shall stand for his life, and thy people for his people," i.e., the destruction to which Benhadad was devoted will fall upon thee and thy people. The expression אישׁ־חרמי (man of my ban) showed Ahab clearly enough what ought to have been done with Benhadad. A person on whom the ban was pronounced was to be put to death (Leviticus 27:29).

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

20:31-43 This encouragement sinners have to repent and humble themselves before God; Have we not heard, that the God of Israel is a merciful God? Have we not found him so? That is gospel repentance, which flows from an apprehension of the mercy of God, in Christ; there is forgiveness with him. What a change is here! The most haughty in prosperity often are most abject in adversity; an evil spirit will thus affect a man in both these conditions. There are those on whom, like Ahab, success is ill bestowed; they know not how to serve either God or their generation, or even their own true interests with their prosperity: Let favour be showed to the wicked, yet will he not learn righteousness. The prophet designed to reprove Ahab by a parable. If a good prophet were punished for sparing his friend and God's when God said, Smite, of much sorer punishment should a wicked king be thought worthy, who spared his enemy and God's, when God said, Smite. Ahab went to his house, heavy and displeased, not truly penitent, or seeking to undo what he had done amiss; every way out of humour, notwithstanding his victory. Alas! many that hear the glad tidings of Christ, are busy and there till the day of salvation is gone.