Catechism of the Catholic Church §827 — excerpt
"Christ, 'holy, innocent, and undefiled,' knew nothing of sin, but came only to expiate the sins of the people. the Church, however, clasping sinners to her bosom, at once holy and always in need of purification, follows constantly the path of penance and renewal."
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.
Whole chapters cited: Hebrews 726
Also cites: LG 8 # 3 · UR 3 · 6 · Paul VI, CPG # 19