There is another set of images that run parallel to those given above: the Church as the Bride of Christ. John the Baptist hinted at it in his final sermon: "He who has the bride is the bridegroom, but the friend of the bridegroom who stands and hears him, rejoices greatly because of the bridegroom's voice. So this joy of mine has been made full" (John 3:29). Later, in responding to the Pharisees, Christ compares His actions to those of a bridegroom (Matthew 9:15) and later analogizes the day of judgment to a marriage feast for the bridegroom (in the parable of the ten virgins, Matthew 25:1-9).
The mystical union -- indeed, the marriage -- of Christ and the Church has its forbears in Jewish literature. "Song of Songs" has long been understood not simply as erotic poetry, of the longing of a lover and His beloved, but also as allegory for God's love of His people. It is for this reason that "Song of Songs" can boast of more commentaries than nearly any other book in the Old Testaments. It was and remains a favorite text of Christian saint, such as the Cistercian abbot St. Bernard of Clairvaux (the 'mellifluous Doctor'), who composed 86 separate sermons on first three chapters "Song of Songs" alone.
The apostle Paul was also prolific in his comparisons between Christ as the bridegroom and the Church as His bride. Paul makes the comparison explicit in Ephesians 5:25-32:
Husbands, love your wives, just as Christ also loved the church and gave Himself up for her, do that He might sanctify her, having cleansed her by the washing of water with the word, that He might present to Himself the church in all her glory, having no spot or wrinkle or any such thing; but that she would be holy and blameless. So husbands ought also to love their own wives as their own bodies. He who loves his own wife loves himself; for no one ever hated his own flesh, but nourishes and cherishes it, just as Christ also does the Church, because we are members of His body. "For this reason a man shall leave his father and mother and shall be joined to his wife, and the two shall become one flesh" [Genesis 2:24]. This mystery is great; but I am speaking with reference to Christ and the Church.It is precisely this imagery, of the Church as the Bride, that is at the heart of Catholic teachings on sexual ethics. After all, marriage is a reenactment writ small of our salvation history, of Christ's mystical union with the body of believers. A number of Christians mystics go further and apply imagery of marriage to the mystical union of the Trinity Itself, of the relation of God to the Son and the Holy Spirit. At the very least, Catholics define marriage as a sacrament, a vessel of God's sanctifying grace, completed through the marital act. Just as Catholics wouldn't dream of using the consecrated hosts of the Eucharist as snack food, so too the Church would teach us not to devalue the 'elements' of marriage: the physical act of sex.
One particular attribute of the Church as Bride deserves mention: its spotlessness. Paul is pretty clear on this score in the passage above, as is St. John the Seer in Revelations 19:7-9:
Let us rejoice and be glad and give glory to Him, for the marriage of the Lamb has come and His bride has made herself ready" It was given to her to clothe herself in fine linen, bright and clean; for the fine linen is the righteousness of the saints. Then he said to me, "Write, 'Bless are those who are invited to the marriage supper of the Lamb.'" And he said to me, "There are the true words of God."This particular imagery, of a Divine bridegroom approaching a pure and spotless Bride, stands in pretty stark contrast with the actual conduct of both Jews and Christians throughout salvation history. God Himself commented on this to the prophet Hosea: "Go, take for yourself a wife of harlotry and have children of harlotry; for the land commits flagrant harlotry, forsaking the Lord" (Hosea 1:2). Through the book, God laments the continued unfaithfulness of His people, yet still promises to redeem her: "Go again, love a woman who is loved by her husband, yet an adulteress, even as the Lord loves the sons of Israel, though they turn to other gods..." (Hosea 3:1). Hosea's marriage to the unfaithful Gomer is a sign of God and His people. Yet Christ's marriage to the spotless Bride is a sign of God and His church.
This is the paradox at the heart of Catholic ecclesiology. As Gomer treated her husband, we who live in Christ treat God pretty abysmally. We are often unfaithful. Yet the Church remains spotless, and while we remain in the Church we remain spotless ourselves. This is why Catholics find the Lutheran dictum simul justus et peccator ("both justified and a sinner") incomprehensible. This is the reason for the Catholic dictum extra Ecclesiam nulla salus: "outside of the Church, there is no salvation."
For the Church is more than the Bride of Christ. She is the Body of Christ as well.