Believe his prophets, i.e. God's promise delivered to us by this prophet, and consequently all other predictions of the prophets that either have been or shall be. So shall ye prosper: take heed, lest by your unbelief you frustrate God's promise.
Related Commentaries of 2 Chronicles 20:20
2 Chronicles 20:20
20 And they rose early in the morning, and went forth into the wilderness of Tekoa: and as they went forth, Jehoshaphat stood and said, Hear me, O Judah, and ye inhabitants of Jerusalem; Believe in the LORD your God, so shall ye be established; believe his prophets, so shall ye prosper.