Thematic Bible: What is not vain

And Moses made an end of speaking all these words to all Israel; And he said to them, Set your hearts to all the words which I testify among you this day, which ye shall command your children to observe to do, all the words of this law. For it is not a vain thing for you: because it is your life; and through this thing ye shall prolong your days in the land whither ye go over Jordan to possess it.