Article V. On the Obligation by Reason of a Promise

279. 1. He who has made an onerous promise to apply Mass, with the intention of binding himself gravely, is bound under grave sin to satisfy this obligation. For example, a priest who, after receiving benefits, promised in thanksgiving and recompense to say Mass for the benefactor accepting this promise is bound to say the Mass. For the most part, such a grave obligation is not present and must not be asserted unless it is certainly established.

2. He who has made a gratuitous promise of saying Mass is indeed bound from fidelity, but only under light sin, and he can satisfy several promises by one Mass, since according to a solidly probable opinion⁴¹⁷ the fruit of the Mass is of infinite value. Hence he who gratuitously promised Peter a Mass for the deceased, Paul a Mass according to his intention, and Andrew likewise a Mass according to his intention, can satisfy all these promises by one sacrifice of the Mass. Thus holds the common opinion.⁴¹⁸

⁴¹⁷ Cf. above, n. 237.

⁴¹⁸ Cf. Noldin-Schmitt, De sacr.¹⁷, n. 199.