Building on the preceding theological base, Paul argued against participating in fornication with prostitutes. The Corinthians had not understood the nature of sexual intercourse or the nature of Christian conversion.
6:15 Another rhetorical question affirmed the truth. As we are members of Christ's body, so our bodies are members of Him. This is not just clever word play. Our physical bodies are just as much a part of Christ--united with Him in a genuine spiritual union--as we are part of the mystical body of Christ, the church. Paul was not speaking here of the believer's union with Christ by becoming members of His mystical body, the church (12:12-26). He was metaphorically speaking of our individual union with Christ's physical body.
When a Christian has sexual relations with a prostitute, he or she takes what belongs to God and gives it to someone else. This is stealing from God. When a Christian marries, this does not happen because God has ordained and approves of marriage (cf. 7:14). He permits us to share our bodies with our lawful mates. Taking a member of Christ and uniting it to a harlot also involves the Lord in that immoral act. Paul's revulsion at the thought of this comes through graphically in his characteristic me genoito(lit. "May it not happen!").
6:16 Paul urged his readers not to think of sexual intercourse as simply a physical linking of two people for the duration of their act. Intercourse involves the whole person, not just the body. It is the most intimate sharing that human beings experience. A spiritual union takes place. Sexual relations affect the inner unseen conditions of the individuals involved very deeply. This is what is in view in the reference to two people becoming "one flesh"in Genesis 2:24. Consequently it is improper to put sexual relations on the same level of significance as eating food.
6:17 In contrast to the union that takes place when two people have sex, the person who trusts Christ unites with Him in an even stronger and more pervasive oneness. This is an even stronger spiritual union. Consequently it is a very serious thing to give to a prostitute what God has so strongly united to Christ.
The argument again contains a chiasm.
AYour bodies are members of Christ's body.
BSo they must not be members of a prostitute's body.
B'Joined to a prostitute your members become one body with her.
A'Joined to Christ your members become one spirit with Him.
