Deuteronomy 31:19-22

19“Now, write this song for yourselves, and teach it to Bnei-Yisrael—put it in their mouth, so that this song may be a witness for Me against Bnei-Yisrael.

20“For when I bring them to the land flowing with milk and honey that I swore to their fathers, and they eat and are satisfied and grow fat—then they will turn to other gods and serve them, and they will spurn Me and break My covenant.

21Now when many evils and troubles have come on them, this song will confront them as a witness; for it will not be forgotten from the mouth of their descendants. For I know the intention they are devising this day, even before I bring them into the land that I swore.”

22That day Moses wrote this song and taught it to Bnei-Yisrael.