Charles Ellicott 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)

If the men come to call you.— The words may be rendered Since (or, because) the men have come to call you. The messengers had already come for that purpose, as it is stated in Numbers 22:16, where the same verb is used. The phrase which is here rendered to “call” occurs also in Numbers 22:5.

Rise up, and go with them.— There is no real inconsistency with Numbers 22:12. The absolute and immutable prohibition had reference to the cursing. The going with the messengers, which was forbidden in mercy at first, was enjoined in judgment at last. God often punishes disobedience to His declared will by permitting the transgressors to “eat the fruit of their own way, and to be filled with their own devices” (Proverbs 1:31). “He gave them their request, but sent leanness into their soul” (Psalms 106:15). (Isaiah 66:4; Jeremiah 2:19).