Catechism of the Catholic Church §857 — excerpt
The Church is apostolic because she is founded on the apostles, in three ways: - she was and remains built on "the foundation of the Apostles," The witnesses chosen and sent on mission by Christ himself; - with the help of the Spirit dwelling in…
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: AG 5 · Roman Missal, Preface of the Apostles I