Charles Ellicott Commentary Numbers 22:18

"And Balaam answered and said unto the servants of Balak, If Balak would give me his house full of silver and gold, I cannot go beyond the word of Jehovah my God, to do less or more." — Numbers 22:18 (ASV)

I cannot go beyond the word of the Lord ... — These words may have been nothing more than an ostentatious semblance of disinterestedness and superiority to worldly considerations; or it is possible that Balaam may have been conscious that “he spoke not of himself,” and that, as regards his prophetic utterances, he was merely the mouthpiece of the Lord.