Catechism of the Catholic Church §1010 — excerpt
Because of Christ, Christian death has a positive meaning: "For to me to live is Christ, and to die is gain." "The saying is sure: if we have died with him, we will also live with him.
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: St. Ignatius of Antioch, Ad Rom., 6, 1-2: Apostolic Fathers, II/2, 217-220
