Moses
Deuteronomy 32:46ESV·traditional attribution

he said to them, “Take to heart all the words by which I am warning you today, that you may command them to your children, that they may be careful to do all the words of this law.

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 the Lord spake unto Moses the selfsame day,.... On which he finished the reading of the law, and the above song, which was the seventh of Adar or February; according to the Targum of Jonathan, the day he died on; according to the Egyptian Calendar (a), it was the sixteenth of that month, see Deu 34:5, saying; as follows. (a) Apud Ludolf. Lex. Ethiop. p. 537.