Paul tells the Corinthians to “flee from sexual immorality. All other sins a person commits are outside the body, but whoever sins sexually, sins against their own body” (1 Corinthians 6:18). In saying that sexual immorality is sin against one’s own body, Paul may have been referencing a common belief among the Greeks of that day that the physical body was not important. In fact, many believed the body to be evil and often described it as a tomb or a weight the soul was forced to carry around. This idea led some in the Corinthian church to take Christian liberty beyond what is appropriate. Why does sexual immorality matter—it’s just a physical act that only involves the body, right? Paul says, “Wrong.”
As Paul confronts the issue of sexual immorality, he builds an argument beginning in 1 Corinthians 6:12. He first establishes the idea that the legality of something is not the only concern. One should ask not just, “Is this permissible for me?” but, “Is this beneficial to myself and others?” Another question is “will this liberty eventually master me, leading to a place of bondage and addiction?”
Paul then addresses the Corinthians’ view of the body in 1 Corinthians 6:13. His readers tended to say, “Food for the stomach and the stomach for food”; that is, “I have an appetite, and it’s not wrong to satisfy it.” Paul responds by saying that both the appetite and the food will be destroyed one day. He then contrasts this to sexual immorality. The body was not designed for immorality in the same way that the stomach was designed for food. Sex is more than a desire to be satisfied; food does not defile a person, but immorality does.
Paul goes on to argue against sexual immorality by pointing to the resurrection. The body will be raised in the same power that “raised the Lord from the dead” (1 Corinthians 6:14). Thus, the body is important, and God still has a plan for the body. It is not an evil that the soul is trapped in, but it is part of the makeup of mankind that God intends to redeem. Both the body and soul will be preserved immortal. So, even if sexual immorality involved only the body, the body is important and intended to glorify the Lord.
Beyond this, the Christian’s body is united to Christ through a spiritual union (1 Corinthians 6:15). What Christians do with their bodies impacts Christ. As the believer is united with Christ, a Christian committing sexual immorality (specifically, in this context, having sex with a prostitute) unites the body of Christ with a prostitute. Paul reacts to this in the most negative way possible in the Greek language, translated, “May it never be!” (1 Corinthians 6:15).
Because of the nature of sexual immorality being against the body, Paul implores the Corinthians to “flee from sexual immorality” (1 Corinthians 6:18). Sexual immorality is the only sin that unites two people in one flesh (verse 16). It is a sin that corrupts and ensnares like no other, and it often leads to physical diseases. For these reasons, Paul concludes that sexual immorality is a sin committed against one’s own body.
The body is the Lord’s and should be used for His glory. Sexual immorality is of particular importance because it is sinning against one’s own body. The believer’s body has been bought by the Lord at a high price and should be treated that way, so flee sexual immorality. Joseph provides a good example of what fleeing sexual immorality looks like (Genesis 39:12).