Catechism of the Catholic Church §175 — excerpt
"We guard with care the faith that we have received from the Church, for without ceasing, under the action of God's Spirit, this deposit of great price, as if in an excellent vessel, is constantly being renewed and causes the very vessel that contains it to be renewed."
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. Irenaeus, Adv. haeres. 3, 24, I: PG 7/1, 966