Treatise I: On the First Precept of the Decalogue

Thou shalt not have strange gods before me...
(Exod. 20:3).

529. The first precept, by forbidding that a false deity be worshiped, prescribes the worship which is owed to the true God. This precept is so general that it already includes the two following in itself. Yet these were proposed explicitly because, for the gravity of the matter, the sanctification of the divine Name and the appointing of a day singularly consecrated to divine worship demanded a special promulgation for themselves (Cat. Rom., on the 1st and 3rd precept, n. 1).

But here there comes to be treated: 1. the virtue of religion in general; 2. the acts of religion commanded by the first precept; 3. the sins opposed to the same precept.