Deuteronomy 31:19

“Now, therefore, write ye this song for you, etc.] Which was now dictated by the Lord, and given to Moses and Joshua to write, which is recorded in (<053201>Deuteronomy 32:1-43): and teach it the children of Israel; teach them by it, instructing them in the meaning of it: thus it was usual in ancient times to write things in verses, that they might be the more pleasingly attended to and regarded, and be longer retained in memory; and especially this practice was used with children, and still is: put it in their mouths; oblige them to get it by heart, or lay it up in their memories, and repeat it frequently, that it may be familiar to them, and not be forgotten by them: that this song may be a…”

“Now therefore write ye this song--National songs take deep hold of the memories and have a powerful influence in stirring the deepest feelings of a people. In accordance with this principle in human nature, a song was ordered to be composed by Moses, doubtless under divine inspiration, which was to be learnt by the Israelites themselves and to be taught to their children in every age, embodying the substance of the preceding addresses, and of a strain well suited to inspire the popular mind with a strong sense of God's favor to their nation.”

“The transaction recorded in these verses may be regarded as the solemn inauguration of Joshua to the office to which he had some time before Numbers 27:22 been called, and his recognition in it by God, which were manifested by his being summoned into the tabernacle with Moses while the Lord appeared in the pillar of cloud (compare Numbers 11:25; Numbers 12:5). Deuteronomy 31:16 The future apostasy of the people is announced in the presence of Joshua that the latter might be fully aware of the danger and strive in his day to avert it. This he faithfully did (compare Joshua 24:31); but we find him in his own last address to Israel repeating Joshua 23:15-16 the self-same prediction and warning.…”

“Write this song - Which is contained Deu. 32:1-43, and is put into a song that it may be better learned, and more fixed in their minds and memories. Put it in their mouths - Cause them to learn it, and sing it one to another, to oblige them to more circumspection. A witness - Of my kindness in giving them so many blessings, of my patience in bearing so long with them, of my clemency in giving them such fair and plain warnings, and my justice in punishing such an incorrigible people. Deuteronomy 31:21”

“31:19-22 When sung by the collective community in days to come, this song (32:1-43) would remind the people of God’s faithfulness in the past and of their too-frequent disloyalty. The major blessings for obedience and curses for disobedience were implicit in the song. The people of Israel would sing it as a sign that they had placed themselves under these promises and threats. Through music, they would be reminded of God’s blessings for obedience and would invoke God’s judgment should they prove unfaithful.”

“this song: Deu 31:22, Deu 31:30, 32:1-43, Deu 32:44, Deu 32:45 and teach it: Deu 4:9, Deu 4:10, Deu 6:7, Deu 11:19 put it in their: Exo 4:15; Sa2 14:3; Isa 51:16, Isa 59:21; Jer 1:9 a witness: Deu 31:21, Deu 31:26; Eze 2:5; Mat 10:18; Joh 12:48 Deuteronomy 31:20”

“"And now," sc., because what was announced in Deu 31:16-18 would take place, "write you this song." "This" refers to the song which follows in ch. 32. Moses and Joshua were to write the song, because they were both of them to strive to prevent the apostasy of the people; and Moses, as the author, was to teach it to the children of Israel, to make them learn it, that it might be a witness for the Lord (for Me) against the children of Israel. "This" is defined still further in Deu 31:20, Deu 31:21 : if Israel, through growing satisfied and fat in its land, which was so rich in costly good, should turn to other gods, and the Lord should visit it in consequence with grievous evils and troubles,…”