Moses
Deuteronomy 32:5BSB·traditional attribution

His people have acted corruptly toward Him; the blemish on them is not that of His children, but of a perverse and crooked generation.

John Calvin Reformed @genevareformer

5. They have corrupted themselves. Moses now inveighs unhesitatingly against the perfidy of the people, and gives loose to the most unmeasured upbraidings; for if God be just and true, then it was plain enough that the Israelites were a depraved and perverse nation.

Matthew Henry Presbyterian @wholebiblehenry

Here is, I. A commanding preface or introduction to this song of Moses, Deu 32:1, Deu 32:2. He begins, 1. With a solemn appeal to heaven and earth concerning the truth and importance of what he was about to say, and the justice of the divine proceedings against a rebellious and backsliding people, for he had said (Deu 31:28) that he would in this song...

Commenting on Deuteronomy 32:1-6

John Gill Reformed Baptist @doctorgill

They have corrupted themselves,.... This and what follows may seem to be the characters of the enemies of Christ, who lightly esteemed and rejected him, set in a contrast with him; who were not only corrupt by nature, as all men are, but were men of corrupt minds in their tenets and principles; who corrupted the word of God by their traditions, in the times...