Numbers 21:13

21:13 From there they moved on and camped on the other side of the Arnon, in the wilderness that extends from the regions of the Amorites, for Arnon is the border of Moab, between Moab and the Amorites.

Numbers 22:36

Balaam Meets Balak

22:36 When Balak heard that Balaam was coming, he went out to meet him at a city of Moab which was on the border of the Arnon at the boundary of his territory.