2 Chronicles 20:10, 23

And now, behold, the children of Ammon and Moab and mount Seir, whom thou wouldest not let Israel invade, when they came out of the land of Egypt, but they turned from them, and destroyed them not

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.