CCC 1371 The Eucharistic sacrifice is also offered for the faithful departed who “have died in Christ but are not yet wholly purified,”1 so that they may be able to enter into the light and peace of Christ:
Put this body anywhere! Don’t trouble yourselves about it! I simply ask you to remember me at the Lord’s altar wherever you are.2
Then, we pray [in the anaphora] for the holy fathers and bishops who have fallen asleep, and in general for all who have fallen asleep before us, in the belief that it is a great benefit to the souls on whose behalf the supplication is offered, while the holy and tremendous Victim is present. .. By offering to God our supplications for those who have fallen asleep, if they have sinned, we. .. offer Christ sacrificed for the sins of all, and so render favorable, for them and for us, the God who loves man.3
1 Council of Trent (1562) DS 1743.
2 St. Monica, before her death, to her sons, St. Augustine and his brother; Conf. 9, 11, 27: PL 32, 775.
3 St. Cyril of Jerusalem, Catech. myst. 5, 9. 10 PG 33, 1116-1117.