Sexual sin is uniquely grave — it is a sin against one's own body in a way other sins are not

"Flee immorality. Every other sin that a man commits is outside the body, but the immoral man sins against his own body." (1 Cor. 6:18) Mike argues this should not be controversial for Christians: not all sin is identical. Sexual sin (fornication, homosexuality, and all sexual immorality outside marriage) has a distinctively grave quality because it violates the body in a way that lying or theft does not. The body is a member of Christ — joining it to sexual immorality is joining Christ's member to immorality.