Rashi on Numbers 22:13/רש"י על במדבר כ״ב:י״ג

1להלך עמכם [THE LORD REFUSES TO GIVE ME LEAVE] TO GO WITH YOU, but only with princes greater than you. This tells us that he was of a proud nature and he did not wish to divulge that he was under the control of the Omnipresent except in arrogant terms (“God will not permit me to go with you”). Consequently (v. 15), ויוסף עוד בלק “Balak sent yet again [more princes, and more honorable than these] (Midrash Tanchuma, Balak 6).