2 Chronicles 20:21-23

When he had consulted with the people, he appointed those who sang to the LORD and those who praised Him in their holy (priestly) attire, as they went out before the army and said, “Praise and give thanks to the LORD, for His mercy and lovingkindness endure forever.” When they began singing and praising, the LORD set ambushes against the sons of Ammon, Moab, and Mount Seir, who had come against Judah; so they were struck down [in defeat]. For the sons of Ammon and Moab [suspecting betrayal] rose up against the inhabitants of Mount Seir, completely destroying them; and when they had finished with the inhabitants of Seir, they helped to destroy one another.