Moses
Numbers 23:5ESV·traditional attribution

And the LORD put a word in Balaam’s mouth and said, “Return to Balak, and thus you shall speak.”

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

And the Lord put a word in Balaam's mouth.... Not grace into his heart, nor the fear of God within him, but suggested to him what to say; impressed it strongly on him, that he could not forget it, and with such power and weight, that he was obliged to deliver it: and said, return unto Balak, and thus shalt thou speak; that is, unto...

Geneva Bible Notes Reformed @genevanotes

And the LORD put a word in Balaam's mouth, and said, Return unto Balak, and thus thou shalt speak. (c) Taught him what to say.