Moses
Numbers 23:8ESV·traditional attribution

How can I curse whom God has not cursed? How can I denounce whom the LORD has not denounced?

Matthew Henry Presbyterian @wholebiblehenry

Here is, I. Great preparation made for the cursing of Israel. That which was aimed at was to engage the God of Israel to forsake them, and either to be on Moab's side or to stand neuter. O the sottishness of superstition, to imagine that God will be at men's beck!

Commenting on Numbers 23:1-12

John Gill Reformed Baptist @doctorgill

How shall I curse whom God hath not cursed?.... The sense is, that it was impossible for him to curse those that God did not curse himself, or would not have cursed by others; not but that he had a good will to it, to get Balak's money and honour, but he knew not how to accomplish it; yea, he saw it was in vain...

Jamieson-Fausset-Brown Reformed @jfbcommentary

How shall I curse, whom God hath not cursed?--A divine blessing has been pronounced over the posterity of Jacob; and therefore, whatever prodigies can be achieved by my charms, all magical skill, all human power, is utterly impotent to counteract the decree of God.