John Gill Commentary Numbers 23:12

"And he answered and said, Must I not take heed to speak that which Jehovah putteth in my mouth?" — Numbers 23:12 (ASV)

And he answered and said
By reply to Balak:

must I not take heed to speak that which the Lord has put in my mouth ?
pretending a great regard to the word of God, and to great carefulness to speak it, exactly and punctually as he received it, whereas he was forced to it, and could not do otherwise.