Catechism of the Catholic Church §991 — excerpt
Belief in the resurrection of the dead has been an essential element of the Christian faith from its beginnings. "The confidence of Christians is the resurrection of the dead; believing this we live."
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: Tertullian, De res, 1,1: PL 2, 841