2 Chronicles 20:23 in the King James Version
For the children of Ammon and Moab stood up against the inhabitants of mount Seir, utterly to slay and destroy them: and when they had made an end of the inhabitants of Seir, every one helped to destroy another.
Context
22 When they began to sing and to praise, the LORD set ambushers against the children of Ammon, Moab, and Mount Seir, who had come against Judah; and they were struck.
23 For the children of Ammon and Moab stood up against the inhabitants of Mount Seir to utterly kill and destroy them. When they had finished the inhabitants of Seir, everyone helped to destroy each other.
24 When Judah came to the place overlooking the wilderness, they looked at the multitude; and behold, they were dead bodies fallen to the earth, and there were none who escaped.