2 Chronicles 20:22-23

22When they began singing and praising, the Lord 1set ambushes against the sons of 2Ammon, Moab, and Mount Seir, who had come against Judah; so they were struck down. 23For the sons of Ammon and Moab rose up against the inhabitants of Mount Seir, completely destroying them; and when they had finished with the inhabitants of Seir, 3they helped to destroy one another.