Catechism of the Catholic Church §1088 — excerpt
"To accomplish so great a work" - the dispensation or communication of his work of salvation - "Christ is always present in his Church, especially in her liturgical celebrations.
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: SC 7