Read 1 Corinthians 6:18 Using Other Translations
Flee fornication. Every sin that a man doeth is without the body; but he that committeth fornication sinneth against his own body.
Flee from sexual immorality. Every other sin a person commits is outside the body, but the sexually immoral person sins against his own body.
Run from sexual sin! No other sin so clearly affects the body as this one does. For sexual immorality is a sin against your own body.