Moses
Deuteronomy 31:20ESV·traditional attribution

For when I have brought them into the land flowing with milk and honey, which I swore to give to their fathers, and they have eaten and are full and grown fat, they will turn to other gods and serve them, and despise me and break my covenant.

John Calvin Reformed @genevareformer

20. But when I shall have brought them. In other words, God again enlarges upon the atrociousness of their iniquity, in that, when He had dealt liberally with the Israelites, they would turn His benefits into occasions of perversity, since nothing can be more base than such ingratitude, he says, then, that He will perform to them, unworthy as they are, that which he has...

Matthew Henry Presbyterian @wholebiblehenry

Here, I. Moses and Joshua are summoned to attend the divine majesty at the door of the tabernacle, Deu 31:14. Moses is told again that he must shortly die; even those that are most ready and willing to die have need to be often reminded of the approach of death.

Commenting on Deuteronomy 31:14-21

John Gill Reformed Baptist @doctorgill

And it shall come to pass, when many evils and troubles are befallen them,.... As did in the times of the judges, in the Babylonish captivity, and do now in their present exile: that this song shall testify against them as a witness; which so clearly points at their sins, with all their aggravated circumstances, and describes so fully their calamities, distresses, and punishment for...