Jamieson, Fausset and Brown on Exodus 20:8

8. Remember the sabbath day--implying it was already known, and recognized as a season of sacred rest. The first four commandments [Ex 20:3-11] comprise our duties to God--the other six [Ex 20:12-17] our duties to our fellow men; and as interpreted by Christ, they reach to the government of the heart as well as the lip (Mt 5:17). "If a man do them he shall live in them" [Le 18:5; Ne 9:29]. But, ah! what an if for frail and fallen man. Whoever rests his hope upon the law stands debtor to it all; and in this view every one would be without hope were not "the Lord our Righteousness" [Jr 23:6; 33:16] (Joh 1:17).