Catechism of the Catholic Church §797 — excerpt
"What the soul is to the human body, the Holy Spirit is to the Body of Christ, which is the Church." "To this Spirit of Christ, as an invisible principle, is to be ascribed the fact that all the parts of the body are joined…
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: St. Augustine, Sermo 267, 4: PL 38, 1231D · Pius XII, encyclical, Mystici Corporis: DS 3808 · St. Irenaeus, Adv. haeres. 3, 24, 1: PG 7/1, 966