That ye should do so in the land. — It should never be forgotten that there is a special connection between the law of Moses and the land of Canaan. It cannot be kept in many of its precepts, except by a chosen people in a protected land.
Related Commentaries of Deuteronomy 4:5
Deuteronomy 4:5
5 Behold, I have taught you statutes and judgments, even as the LORD my God commanded me, that ye should do so in the land whither ye go to possess it.