Catechism of the Catholic Church §1689 — excerpt
The Eucharistic Sacrifice. When the celebration takes place in church the Eucharist is the heart of the Paschal reality of Christian death. In the Eucharist, the Church expresses her efficacious communion with the departed: offering to the Father in the Holy Spirit the sacrifice of…
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: OCF 41 · OCF 57