2 Chronicles 20:21-23

After talking it over with the people, Jehoshaphat appointed a choir for GOD; dressed in holy robes, they were to march ahead of the troops, singing, Give thanks to GOD, His love never quits. As soon as they started shouting and praising, GOD set ambushes against the men of Ammon, Moab, and Mount Seir as they were attacking Judah, and they all ended up dead. The Ammonites and Moabites mistakenly attacked those from Mount Seir and massacred them. Then, further confused, they went at each other, and all ended up killed.