1 Kings 22:29 - Albert Barnes' Notes on the Bible

It might have been expected that Jehoshaphat would have withdrawn from the expedition when he heard Micaiah denounce it. He had, however, rashly committed himself to take part in the war by a solemn promise, before he bethought himself of inquiring what was the will of God in the matter. Now he was ashamed to draw back, especially as Ahab, whom the prophecy chiefly threatened, was resolved to brave it. He may also have had a personal affection for Ahab, and so have been loth to desert him in his need. Compare 2 Chronicles 19:2.