Charles Ellicott Commentary Numbers 22:36

"And when Balak heard that Balaam was come, he went out to meet him unto the City of Moab, which is on the border of the Arnon, which is in the utmost part of the border." — Numbers 22:36 (ASV)

A city of Moab. —Better, the city of Moab. .

Which is in the utmost coast. —Or, which flows at the extremity of the border. Sihon, the Amorite, had taken possession of the Moabite territory as far as the Arnon.