Moses
Deuteronomy 32:48ESV·traditional attribution

That very day the LORD spoke to Moses,

John Calvin Reformed @genevareformer

48. And the Lord spake unto Moses. We infer that this is not recorded in its regular order, because it is certain that Moses was warned of his approaching death before the Song was composed; and this the second passage, which I have here appended, expressly confirms; for he says that, before he substituted Joshua for himself, the place was pointed out to him in which he was to die.

Matthew Henry Presbyterian @wholebiblehenry

Here is, I. The solemn delivery of this song to the children of Israel, Deu 32:44, Deu 32:45. Moses spoke it to as many as could hear him, while Joshua, in another assembly, at the same time, delivered it to as many as his voice would reach.

Commenting on Deuteronomy 32:44-52

John Gill Reformed Baptist @doctorgill

And die in the mount whither thou goest up,.... Immediately after having taken a view of the land, expect to die, prepare for it, and willingly and cheerfully submit to it: and be gathered unto thy people; to the spirits of just men made perfect in heaven, his more immediate and more remote ancestors, the souls of good men; for otherwise there were none that...