John Wesley on Numbers 22:22

Because he went - Because he went of his own accord, with the princes of Moab, and did not wait till they came to call him, which was the sign and condition of God's permission, but rather himself rose and called them. The apostle describes Balaam's sin here to be, that he ran greedily into an error for reward, Jude 1:11. For an adversary - To oppose, if not to kill him. His servants with him - The rest of the company being probably gone before them. For in those ancient times there was more of simplicity, and less of ceremony, and therefore it is not strange that Balaam came at some distance, after the rest, and attended only by his own servants.