Catechism of the Catholic Church §2075 — excerpt
"What good deed must I do, to have eternal life?" - "If you would enter into life, keep the commandments" (Mt 19:16-17).
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.