CCC 738 Thus the Church’s mission is not an addition to that of Christ and the Holy Spirit, but is its sacrament: in her whole being and in all her members, the Church is sent to announce, bear witness, make present, and spread the mystery of the communion of the Holy Trinity (the topic of the next article):
All of us who have received one and the same Spirit, that is, the Holy Spirit, are in a sense blended together with one another and with God. For if Christ, together with the Father’s and his own Spirit, comes to dwell in each of us, though we are many, still the Spirit is one and undivided. He binds together the spirits of each and every one of us,. .. and makes all appear as one in him. For just as the power of Christ’s sacred flesh unites those in whom it dwells into one body, I think that in the same way the one and undivided Spirit of God, who dwells in all, leads all into spiritual unity.1
1 St. Cyril of Alexandria, In Jo. ev., 11,11: PG 74, 561.