Numbers 21:13-15

13From there they journeyed and camped on the other side of the Arnon, which is in the wilderness that comes out of the border of the Amorites; 1for the Arnon is the border of Moab, between Moab and the Amorites. 14For that reason it is said in the Book of the Wars of the Lord, “Waheb in Suphah, And the 2wadis of the Arnon,15And the slope of the wadis That extends to the site of 3Ar, And leans to the border of Moab.”