Catechism of the Catholic Church §77 — excerpt
"In order that the full and living Gospel might always be preserved in the Church the apostles left bishops as their successors. They gave them their own position of teaching authority."
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: DV 7 # 2 · St. Irenaeus, Adv. haeres. 3, 3, 1: PG 7/1, 848 · Harvey, 2, 9 · DV 8 # 1