1 Corinthians 6:15-18 (KJV)
15 Know ye not that your bodies are the members of Christ? shall I then take the members of Christ, and make them the members of an harlot? God forbid.
16 What? know ye not that he which is joined to an harlot is one body? for two, saith he, shall be one flesh.
17 But he that is joined unto the Lord is one spirit.
18 Flee fornication. Every sin that a man doeth is without the body; but he that committeth fornication sinneth against his own body.