Catechism of the Catholic Church §761 — excerpt
The gathering together of the People of God began at the moment when sin destroyed the communion of men with God, and that of men among themselves.
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: Acts 13 · Acts 16
Also cites: LG 9