2 Chronicles 20:20-23

They were up early in the morning, ready to march into the wilderness of Tekoa. As they were leaving, Jehoshaphat stood up and said, “Listen Judah and Jerusalem! Listen to what I have to say! Believe firmly in GOD, your God, and your lives will be firm! Believe in your prophets and you’ll come out on top!” 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.