Passage
Now therefore write ye this song for you, and teach it the children of Israel: put it in their mouths, that this song may be a witness for me against the children of Israel.
Now therefore write ye this song for you, and teach it the children of Israel: put it in their mouths, that this song may be a witness for me against the children of Israel.
Deuteronomy 31:17 Then my anger shall be kindled against them in that day, and I will forsake them, and I will hide my face from them, and they shall be devoured, and many evils and troubles shall befall them; so that they will say in that day, Are not these evils come upon us, because our God is not among us?
Deuteronomy 31:18 And I will surely hide my face in that day for all the evils which they shall have wrought, in that they are turned unto other gods.
Deuteronomy 31:19 Now therefore write ye this song for you, and teach it the children of Israel: put it in their mouths, that this song may be a witness for me against the children of Israel.
Deuteronomy 31:20 For when I shall have brought them into the land which I sware unto their fathers, that floweth 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 provoke me, and break my covenant.
Deuteronomy 31:21 And it shall come to pass, when many evils and troubles are befallen them, that this song shall testify against 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.
The verse centers on "therefore", "write", "song", "teach", "children", "israel", and "mouths". It is saying that the verse draws attention to "therefore" and "write", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 18's "And I will surely hide my face..." into verse 20's "For when I shall have brought them...", so "therefore" and "write" belong inside that flow. In Deuteronomy context, the local focus is covenant, worship, and faithfulness.
A plain takeaway is to answer the verse's own emphasis on "therefore" and "write" with trust shaped by these words, not by a vague optimism outside the passage.