Article I. On the Obligation of Celebrating by Reason of the Priesthood

I say. All priests, by reason of the priesthood, by divine right are held under grave sin to celebrate at some time. This is proved from the words of Christ, Luke xxii, 19: "Do this in remembrance of Me." - By these words, according to the witness of the Council of Trent, Christ commanded the Apostles and their successors that they should offer the sacrifice. Besides, all priests in their ordination receive not only the power, but also the charge and office of sacrificing annexed to it. Hence the Apostle says, Heb. v, 1: "For every high priest taken from among men is appointed for men in those things which pertain to God, that he may offer gifts and sacrifices for sins." Now in a grave matter each one is held under grave sin to carry out the charge he has received. - Cf. St. Thomas, 3, q. 82, art. 10. - St. Alphonsus, n. 313.

The Code says: All priests are held by the obligation of offering the Sacrifice several times per year ... (Can. 805).

Question. How often in life or in a year is a priest held to celebrate?

Resp. Let the Bishop or religious Superior take care ... that the same priests operate in divine things at least on individual Sundays and other feasts of precept (Can. 805).