1 Corinthians 6:19
6:19 your body. This is the classic verse which teaches that a Christian’s body belongs to God, not to himself or herself (modern “pro-choice” feminists notwithstanding). Since our “bodies are the members of Christ” (I Corinthians 6:15), we have no right to unite them with some other body in any sexual relation outside of monogamous marriage. Such becomes a sin “against his own body” (I Corinthians 6:18), which could easily result in one of many sex-transmitted diseases (only the worst of which is AIDS), not to mention psychological disorders.