John Calvin Commentary Numbers 22:20

"And God came unto Balaam at night, and said unto him, If the men are come to call thee, rise up, go with them; but only the word which I speak unto thee, that shalt thou do." — Numbers 22:20 (ASV)

And God came to Balaam at night. Although God is far from being deceitful, hypocrites with their quibbles still deserve for Him to confound their schemes. If we consider Balaam's desire more closely, it was that God should contradict Himself. For if he was persuaded that God was truthful, what else could he hope for, except that God would confirm His reply ten times over? Nevertheless, Balaam wickedly lies to God when he asks for permission to go—a request that would convict God Himself of capriciousness and inconstancy. God, therefore, ironically permits what He had previously forbidden.

If anyone should think it absurd that God, who is truth itself, should speak deceptively, the answer is easily found. Namely, God was guilty of no falsehood; rather, He loosened the reins on a man obstinate in his own perverseness. This is just as a person might release a wayward and grossly immoral son from his authority because the son refuses to be ruled. For if Balaam’s ungodly covetousness had not blinded him, the meaning of this ironical permission would not have been difficult to understand.

Therefore, let hypocrites learn that they profit nothing by their vain pretenses, even though God may indulge them for a time, since He ultimately takes the wily in their own craftiness. For this reason, nothing is better than to inquire, with pure and simple teachableness, what He would have us do, so that we may instantly yield and not try to alter a word or a syllable as soon as He has seen fit to open His holy mouth to instruct us. For to call into question what He has decided—what is it but to compel Him by our insistence to bend to our wishes?