Catechism of the Catholic Church §815 — excerpt
What are these bonds of unity? Above all, charity "binds everything together in perfect harmony." But the unity of the pilgrim Church is also assured by visible bonds of communion: - profession of one faith received from the Apostles; -common celebration of divine worship, especially…
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: UR 2 · LG 14 · CIC, can. 205