II Chronicles 20:20-23

So they rose early in the morning and went out into the Wilderness of Tekoa; and as they went out, Jehoshaphat stood and said, “Hear me, O Judah and you inhabitants of Jerusalem: Believe in the LORD your God, and you shall be established; believe His prophets, and you shall prosper.” And when he had consulted with the people, he appointed those who should sing to the LORD, and who should praise the beauty of holiness, as they went out before the army and were saying: “Praise the LORD, For His mercy endures forever.” Now when they began to sing and to praise, the LORD set ambushes against the people of Ammon, Moab, and Mount Seir, who had come against Judah; and they were defeated. For the people of Ammon and Moab stood up against the inhabitants of Mount Seir to utterly kill and destroy them. And when they had made an end of the inhabitants of Seir, they helped to destroy one another.