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
1 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.