Deuteronomy 31:19-23

19Now therefore write ye this song for you, and teach thou it the children of Israel: put it in their mouths, that this song may be a witness for me against the children of Israel.

20For when I shall have brought them into the land which I sware unto their fathers, flowing with milk and honey; and they shall have eaten and filled themselves, and waxen fat; then will they turn unto other gods, and serve them, and despise me, and break my covenant.

21And it shall come to pass, when many evils and troubles are come upon them, that this song shall testify before them as a witness; for it shall not be forgotten out of the mouths of their seed: for I know their imagination which they go about, even now, before I have brought them into the land which I sware.

22So Moses wrote this song the same day, and taught it the children of Israel.

23And he gave Joshua the son of Nun a charge, and said, Be strong and of a good courage: for thou shalt bring the children of Israel into the land which I sware unto them: and I will be with thee.