19 Now therefore, write down this song for yourselves, and teach it to the children of Israel; put it in their mouths, that this song may be a witness for Me against the children of Israel. 20 When I have brought them to the land flowing with milk and honey, of which I swore to their fathers, and they have eaten and filled themselves and grown fat, then they will turn to other gods and serve them; and they will provoke Me and break My covenant. 21 Then it shall be, when many evils and troubles have come upon them, that this song will testify against them as a witness; for it will not be forgotten in the mouths of their descendants, for I know the inclination of their behavior today, even before I have brought them to the land of which I swore to give them."
22 Therefore Moses wrote this song the same day, and taught it to the children of Israel.
Matthew Henry's Commentary on Deuteronomy 31:19-22
Commentary on Deuteronomy 31:14-22
(Read Deuteronomy 31:14-22)
Moses and Joshua attended the Divine Majesty at the door of the tabernacle. Moses is told again that he must shortly die; even those who are most ready and willing to die, need to be often reminded of its coming. The Lord tells Moses, that, after his death, the covenant he had taken so much pains to make between Israel and their God, would certainly be broken. Israel would forsake Him; then God would forsake Israel. Justly does he cast those off who so unjustly cast him off. Moses is directed to deliver them a song, which should remain a standing testimony for God, as faithful to them in giving them warning, and against them, as persons false to themselves in not taking the warning. The word of God is a discerner of the thoughts and intents of men's hearts, and meets them by reproofs and correction. Ministers who preach the word, know not the imaginations of men; but God, whose word it is, knows perfectly.