Albert Barnes Commentary Numbers 22:35

"And the angel of Jehovah said unto Balaam, Go with the men; but only the word that I shall speak unto thee, that thou shalt speak. So Balaam went with the princes of Balak." — Numbers 22:35 (ASV)

Go with the men – A command, not merely a permission. Balaam, no longer a faithful servant of God, was from then on overruled in all his acts so that he might serve the divine purpose as an instrument (Numbers 22:26).

A city of Moab – Or, Ir-Moab, probably the same as Ar-Moab (Numbers 21:15). As Balaam in his journey would avoid the districts occupied by the Israelites, he must have approached this city from the east, by the course of the Nahaliel; and in the name Balu’a, still borne by one of the upper branches of this stream, there is perhaps a reminiscence of the name of the prophet.