'Mouths' in the Bible

And now, write ye this song, 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.

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.