CCC 808 The Church is the Bride of Christ: he loved her and handed himself over for her. He has purified her by his blood and made her the fruitful mother of all God’s children.
CCC 796 The unity of Christ and the Church, head and members of one Body, also implies the distinction of the two within a personal relationship. This aspect is often expressed by the image of bridegroom and bride. The theme of Christ as Bridegroom of the Church was prepared for by the prophets and announced by John the Baptist. The Lord referred to himself as the “bridegroom.” The Apostle speaks of the whole Church and of each of the faithful, members of his Body, as a bride “betrothed” to Christ the Lord so as to become but one spirit with him. The Church is the spotless bride of the spotless Lamb. “Christ loved the Church and gave himself up for her, that he might sanctify her.” He has joined her with himself in an everlasting covenant and never stops caring for her as for his own body:
This is the whole Christ, head and body, one formed from many . . . whether the head or members speak, it is Christ who speaks. He speaks in his role as the head (ex persona capitis) and in his role as body (ex persona corporis). What does this mean? “The two will become one flesh. This is a great mystery, and I am applying it to Christ and the Church.” And the Lord himself says in the Gospel: “So they are no longer two, but one flesh.” They are, in fact, two different persons, yet they are one in the conjugal union, . . . as head, he calls himself the bridegroom, as body, he calls himself “bride.”
CCC 789 The comparison of the Church with the body casts light on the intimate bond between Christ and his Church. Not only is she gathered around him; she is united in him, in his body. Three aspects of the Church as the Body of Christ are to be more specifically noted: the unity of all her members with each other as a result of their union with Christ; Christ as head of the Body; and the Church as bride of Christ.