Catechism of the Catholic Church §1815 — excerpt
The gift of faith remains in one who has not sinned against it. But "faith apart from works is dead": when it is deprived of hope and love, faith does not fully unite the believer to Christ and does not make him a living member of his Body.
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: Council of Trent (1547): DS 1545