Catechism of the Catholic Church §769 — excerpt
"The Church . . will receive its perfection only in the glory of heaven," at the time of Christ's glorious return. Until that day, "the Church progresses on her pilgrimage amidst this world's persecutions and God's consolations."
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: LG 48 · St. Augustine, De civ. Dei, 18, 51: PL 41, 614 · LG 8 · LG 5 · 6 · LG 2