What is a sin outside the body (1 Corinthians 6:18)?

In 1 Corinthians 6:18–20, the apostle Paul summarizes his teaching on the gravity of sexual sin. He writes, “Flee from sexual immorality. All other sins a person commits are outside the body, but whoever sins sexually, sins against their own body. Do you not know that your bodies are temples of the Holy Spirit, who is in you, whom you have received from God? You are not your own; you were bought at a price. Therefore honor God with your bodies.”

Paul’s statement that “all other sins a person commits are outside the body” is an interesting expression that requires careful interpretation. Some Bible scholars believe Paul is quoting a Corinthian slogan—a claim that “every sin a person commits is outside the body.” If true, Paul may be using a diatribe-style argument, imagining a conversation between himself and his Corinthian audience. He is directly challenging their belief that sin occurs outside the body, asserting that the one who commits sexual sin is indeed sinning against his own body.

An ancient Greek philosophical belief held that sin and evil reside only in the physical realm of human existence, while the internal spiritual dimension remains pure and untouched by bodily actions. The Corinthians seem to have embraced this idea to justify sexual freedom, arguing that sin concerns only the soul and its intentions. This viewpoint renders bodily appetites and their satisfaction morally irrelevant. “Sin outside the body” was equivalent to saying that sin is merely physical and doesn’t affect the spirit or soul.

Paul clearly rejects this concept, insisting that sexual sin penetrates inward, affecting oneself and one’s partner (Proverbs 6:32; 1 Corinthians 6:15–16). Sexual activity cannot be limited to the physical realm or considered spiritually neutral. Rather, it affects the whole person.

Paul’s theological point and central concern is that the physical body houses the Holy Spirit. This makes sexual sin a violation that pollutes the individual in whom the Spirit of Christ dwells. Moreover, Christians are one with Christ. Paul states, “But the person who is joined to the Lord is one spirit with him” (1 Corinthians 6:17, NLT; see also John 17:20–23; Colossians 3:3; Galatians 2:20). The believer’s body “is not meant for sexual immorality but for the Lord, and the Lord for the body” (1 Corinthians 6:13; see also Romans 12:1).

For Paul, the seriousness of sexual sin stems from its all-inclusive nature. When two people engage in sexual intercourse, they become one flesh (Genesis 2:24; 1 Corinthians 6:16; Matthew 19:4–6). If one partner belongs to Christ through baptism, that believer is misusing a body that belongs to Christ when they sin. The incompatibility between an immoral sexual union and the believer’s union with Christ, combined with the body’s status as the temple of the Holy Spirit, is significant. It makes sexual sin an offense against both Christ and the sanctity of that temple. Thus, Paul asks, “Don’t you realize that your body is the temple of the Holy Spirit, who lives in you and was given to you by God? You do not belong to yourself” (1 Corinthians 6:19, NLT; see also 1 Corinthians 3:16–17).

Paul uses the Greek word sōma, translated as “body,” to emphasize that the believer’s physical body belongs to Christ and serves as a temple of the Holy Spirit (1 Corinthians 6:18–19). The person who sins sexually sins not only against his own body but against the whole body of Christ (1 Corinthians 12:12–27; Romans 12:4–5). The behavior of each individual member of Christ’s body affects the spiritual life of the entire church.

Instead of saying there is sin that exists outside the body, Paul wants believers to understand that no other sin so clearly affects the body as sexual sin. It touches the whole person and the entire body of Christ. Whether sexual or otherwise, sin has widespread and eternal consequences (Romans 5:12; 1 Corinthians 6:10). Thankfully, through the grace and forgiveness of God, we can be wholly transformed so that we no longer pursue a habitual life of sin but live for God’s kingdom and glory (Romans 6:6-7, 11–14; 1 Corinthians 6:11; 1 John 3:9; 1 Peter 2:24; 4:1–2). When we do fall short and give in to temptation, we can confess our sins to God, who “is faithful and just to forgive us our sins and to cleanse us from all wickedness” (1 John 1:9, NLT).