Chapter 26 — Part III: The Decalogue — The Third Commandment
Section 7. This Commandment about the observance of the Sabbath, on the other hand, considered as to the time appointed for its fulfilment, is not fixed and unalterable, but susceptible of change, and belongs not to the moral, but the ceremonial law. Neither is it a principle of the natural law; we are not instructed by nature to give external worship to God on that day, rather than on any other. And in fact the Sabbath was kept holy only from the time of the liberation of the people of Israel from the bondage of Pharaoh. The observance of the Sabbath was to be abrogated at the same time as the other Hebrew rites and ceremonies, that is, at the death of Christ. Having been, as it were, images which foreshadowed the light and the truth, these ceremonies were to disappear at the coming of that light and truth, which is Jesus Christ. Hence St. Paul, in his Epistle to the Galatians, when reproving the observers of the Mosaic rites, says: You observe days and months and times and years; I am afraid of you lest perhaps I have laboured in vain amongst you. And he writes to the same effect to the Colossians.