NET

21 Then when many disasters and distresses overcome them this song will testify against them, for their descendants will not forget it. I know the intentions they have in mind today, even before I bring them to the land I have promised.”

Darby

21 And it shall come to pass, when many evils and troubles have 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 are forming already this day, before I bring them into the land which I have sworn [unto them].

KJV

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.