John Gill Commentary Numbers 23:2

"And Balak did as Balaam had spoken; and Balak and Balaam offered on every altar a bullock and a ram." — Numbers 23:2 (ASV)

And Balak did as Balaam had spoken
Ordered seven altars to be built, and prepared seven bullocks and rams for sacrifice:

and Balak and Balsam offered on every altar a bullock and a ram ;
Both seem to be concerned in offering the sacrifices; Balak, though a king, it being usual for kings to be priests also, as Melchizedek was, and Balaam as a prophet.

And these sacrifices were offered to the true God, as seems clear from (Numbers 23:4) and to which Balak, at the direction of Balaam, agreed, in order to gain the Lord on his side, that he might prevail over the people of Israel.