Flee sexual immorality. Every sin that a man does is outside the body, but he who commits sexual immorality sins against his own body. (1 Corinthians 6:18, NKJV)
Every sin we commit begins in the mind (“outside the body”), as Jesus taught in Mark 7:20-23 (see Matt. 5:27-28). Therefore, control the mind; control the body. Sexual immorality (porneia, fornication) is antagonistic to the purpose God gave our bodies –which is to give glory to God (1 Cor. 6:19-20). When sexual activity occurs outside of God-endorsed marriage, it is not love; it is dishonorable in His sight. This is God’s judgment, since He said, “Marriage is honorable among all, and the bed undefiled; but fornicators and adulterers God will judge” (Heb. 13:4). Christians are “joined to the Lord,” therefore, we must not join ourselves to a harlot (1 Cor. 6:16-18). Christ calls us to keep our minds and our bodies pure, so that we may serve the Lord in holiness, not moral defilement. “As He who called you is holy, you also be holy in all your conduct, because it is written, Be holy, for I am holy” (1 Pet. 1:15-16).