Catechism of the Catholic Church §336 — excerpt
From infancy to death human life is surrounded by their watchful care and intercession. "Beside each believer stands an angel as protector and shepherd leading him to life."
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. Basil, Adv. Eunomium III, I: PG 29, 656B