Flee sexual immorality. Every sin that a man does is outside the body, but he who commits sexual immorality sins against his own body.
It seems the Corinthians used an analogy to try to justify sexual immorality, making it just another bodily function: “Foods for the stomach and the stomach for foods” (1 Corinthians 6:13). Paul strongly disagreed. “Now the body is not for sexual immorality but for the Lord” (verse 13).
Paul explained that our bodies are members of Christ, and so we must not make them members of a harlot (verse 15). Our bodies are the temple of the Holy Spirit, paid for by Christ’s sacrifice, and so we are not our own (verses 19-20). We must glorify God in our body and spirit (verse 20), not disgust Him by doing things He hates.
Verse 18 is true on several levels. Sexual immorality hurts us by robbing us of some of the true joys of committed marital love. It also can increase the risks of sexually transmissible diseases—another sin against our own bodies. But most of all it is being unfaithful to God—a sin that carries the penalty of eternal death.
No wonder Paul told the Corinthians to flee! In our sex-saturated modern society, the warning and advice apply as well.
For more about avoiding sexual sin, see the article “Seventh Commandment: You Shall Not Commit Adultery.”