Catechism of the Catholic Church §1330 — excerpt
The memorial of the Lord's Passion and Resurrection. The Holy Sacrifice, because it makes present the one sacrifice of Christ the Savior and includes the Church's offering.
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.
Whole chapters cited: 1 Peter 25