Sex and Union with Christ

Union with Christ is the profound and mysterious description of the reality of the elect believer’s gracious salvation. All men by nature are in connection with Adam. In Adam, all are conceived and born dead in sin. In Adam, all perish. In Christ, all his people are made alive. He is the last Adam, the head of the new human race. In him alone is life and salvation. To be united to Christ is salvation. There is an eternal connection with Christ because we are chosen in him in the decree of election. Because we are eternally his, Christ died at the cross in the place of and as the representative of his elect people and paid their redemption price. In time every one of God’s elect people are graciously and really united to Christ by the work of the Holy Spirit so that they become bone of his bone and flesh of his flesh. We are made one with him by faith. Faith is essentially the union of the believer with Christ. By that faith, the elect are partakers of all of Christ’s riches and gifts.
1 Corinthians 6:13–20 speaks about the believer’s union with Christ and makes a practical application of that truth to sex. There are many practical—pragmatic—reasons not to have sex before marriage. The Bible speaks about these too. You will destroy your body with a disease, have a child in your teen years, ruin a reputation, or wreck your finances. But there is a profounder reason: you are joined with Christ, a member of his body. Will you pollute the body of Christ with fornication?
The believer is joined with Christ. The Apostle asks the question, “Know ye not that your bodies are the members of Christ?” (v.15). So he teaches that not only is our soul joined with Christ, but also our body. Christ saves the believer body and soul. God saves by uniting the believer body and soul to Christ. The believer in his body will be raised from the dead in the day of Jesus Christ. In heaven, the body will be the perfect instrument for the praise and glory of God. So in this life already the body must be the instrument for the Christian’s new life in Christ.
The Apostle continues speaking about union with Christ when he says, “But he that is joined unto the Lord is one spirit” (v.17). The deep reality of the believer’s union with Christ is a one spirit union. The analogy is to an earthly marriage. In an earthly marriage, God makes a man and a woman one flesh. In our union with Christ, God makes the believer one spirit with Christ. The spirit mentioned there is the Holy Spirit as the Spirit of Christ. So the Apostle goes on to ask, “What? Know ye not that your body is the temple of the Holy Ghost which is in you?” (v.19). Being one spirit with Christ we are indwelt by the Spirit of Christ who makes of us his temple, brings Christ to us and makes us one with Christ.
The important point the Apostle is making in all of this is that the believer’s body is Christ’s, the body is joined to Christ, the body is indwelt by the Spirit of Christ, the body is one with Christ, and in the body the believer is to be for Christ.
Since the body is Christ’s the body is not for fornication. The Apostle says, “Now the body is not for fornication, but for the Lord” (v.13). God did not make the body and redeem the body so that the body can be used for fornication. God made and redeemed the body to be an instrument to serve the Lord. Then he adds something surprising, “And the Lord for the body” (v.13). God made the Lord Jesus Christ. He made the Lord Jesus Christ in the wonder of the incarnation, his perfect obedience, his atoning death, and the miracle of the resurrection. By the resurrection in particular he made Jesus both Lord and Christ. By the wonder of union with Christ, he made Jesus our Lord really and spiritually. He did not do all that so that the body can be used for fornication.
Fornication is a sin against the seventh commandment. It includes any unlawful sexual activity outside the marriage bond. Sex is not the evil. Sex in marriage is good. Sex outside of marriage is evil. It is fornication. The apostle mentions one form of fornication when he says, “joined to an harlot” (v.16). The young men of Corinth would buy a prostitute to satisfy their lusts. Today one has to mention the epidemic of pornography that plagues the young men and the young women of the churches. Men—and women, too—join themselves to filthy harlots in books, magazines, on phones, tablets, computers, and through video game consoles by means of their eyes, imaginations, and self-gratifying activities. By the word fornication, then, the Apostle means any and all sexual activity by the young person before marriage. All that leads up to sex— including filthy dancing—and all that entices to sex—including suggestive gestures and provocative dressing—is included in the word fornication.
Fornication is a sin with and against the body. The Spirit says, “Every sin that a man doeth is without the body; but he that committeth fornication sinneth against his own body” (v.18). Fornication is a sin with the body. Fornication is an abuse of the body. Fornication is a sin against the body. The sin of fornication in a peculiar way defiles and degrades that body. But the body is Christ’s so the fornicator sin’s with and so defiles and degrades a member of Christ.
Fornication also gives that body to another. He explains when he says, “What? Know ye not that he which is joined to an harlot is one body? For two, saith he, shall be one flesh” (v.16). In the act of sex, one is joined to another in a dark, devilish, and fleshly imitation of marriage. As in a marriage sex outside of marriage is a sin against the spouse, so the Christian young person joined to Christ sins against Christ. The Christian young person takes a member of Christ—his body—and gives that member of Christ to a harlot. The Christian young person by fornication is joined to the harlot and so pollutes that member of Christ—the body—by the harlot. So it is with all fornication. By the particular act of fornication—pornography, sex before marriage, sexually activity of any kind—the believer defiles the member of Christ and sins against Christ.
Because fornication is a sin with the body, and the body is the temple of the Holy Ghost in the believer’s union with Christ, the fornicator is also sacrilegious desecrator of the Holy Spirit’s temple. It is as though a Jew in Solomon’s day walked into the newly consecrated temple and smeared pig fat all over the floor, walls, and furniture. So the fornicator defiles the Spirit’s temple by fornication in a shocking affront to the Spirit and the Lord who is that temple by his Spirit.
The calling is to “flee fornication” (v.18). Flee the sin and every opportunity or temptation to it. It is not a sin to which the Christian young person can come close and not fall. The wise Father asks his son a rhetorical question about fornication: “Can a man take fire in his bosom, and his clothes not be burned” (Prov. 6:27)? The young person must flee and get as far away as possible. For the Christian young person who has committed fornication, flee from it to the cross of Jesus Christ for forgiveness to take away the guilt, shame, and defilement of that sin. Over against the desires for sex and temptations to fornication, flee to the cross of Christ for the power of the cleansing blood of Jesus Christ to deliver from the power and dominion of that sin. The Christian young person is not a slave to his passions, lusts, and desires, but is the possession of Jesus Christ his Lord and in Christ, there is grace to flee that sin and rule over those passions.
The calling also is “glorify God in your body” (v.20). The Apostle adds, “in your spirit,” because such a sanctified walk begins in the spirit and carries through to the body (v.20). The believer lives in light of the reality that he is joined to Christ and indwelt by the Spirit. Knowing that, he honors that in his body. Glorifying God in your body is the sanctified use of the body in one’s calling now and abstaining from all sexual activity until marriage. Sex is not the sin. Fornication is the sin. Flee fornication. Glorify God in your bodies.