TREATISE III: On the Third Precept of the Decalogue

Remember that thou sanctify the day of the Sabbath.
(Exod., 20, 8).

651. The impediments of true religion having been removed through the first and second precept, and various services of reverence and fidelity which are owed to God having been assigned, there now comes the third precept, directly affirmative, which prescribes external worship as a corollary of the preceding precepts.

No one does not see that this divine worship is the foundation of morality, and therefore of Christian society. Therefore the noble and chief office of princes and rulers of societies will always be, in ordering and imposing worship, to assist the presidents of the Church by their authority, and to command the people to obey the precepts of priests (Catech. Rom., de 3 Praec., n. 2).

We shall treat: 1. of feasts to be sanctified in general; 2. of the obligation of abstaining from servile works; 3. of the obligation of hearing Mass.