God gave man and woman the joy and pleasure of sexual relations within the bounds of marriage, and the Bible is clear about the importance of maintaining sexual purity within the boundaries of that union between man and wife (Ephesians 5:31). Humans are well aware of the pleasing effect of this gift from God but have expanded it well beyond marriage and into virtually any circumstance. The secular world’s philosophy of “if it feels good, do it” pervades cultures, especially in the West, to the point where sexual purity is seen as archaic and unnecessary.
Yet look at what God says about sexual purity. “You should be sanctified: that you should avoid sexual immorality; that each of you should learn to control his own body in a way that is holy and honorable, not in passionate lust like the heathen, who do not know God.” “For God did not call us to be impure, but to live a holy life” (1 Thessalonians 4:3–5, 7). This passage outlines God’s reasons for calling for sexual purity in the lives of His children.
First, we are “sanctified” and for that reason, we are to avoid sexual immorality. The Greek word translated “sanctified” means literally “purified, made holy, consecrated [unto God].” As Christians, we are to live a purified life because we have been made holy by the exchange of our sin for the righteousness of Christ on the cross and have been made completely new creations in Christ (2 Corinthians 5:17–21). Our old natures, with all their impurities, sexual and otherwise, have died and now the life we live, we live by faith in the One who died for us (Galatians 2:20). To continue in sexual impurity (fornication) is to deny that and doing so is, in fact, a legitimate reason to question whether we have ever truly been born again. Sanctification, the process by which we become more and more Christlike, is an essential evidence of the reality of our salvation.
We also see in 1 Thessalonians 4:3–5 the necessity of controlling our bodies. When we give in to sexual immorality, we give evidence that the Holy Spirit is not indwelling us because we do not possess one of the fruits of the Spirit—self-control. All believers display the fruit of the Spirit (Galatians 5:22–23) to a greater or lesser degree depending on the length of time they have walked with God. Uncontrolled “passionate lust” is a work of the flesh (Galatians 5:19), not of the Spirit. So controlling our lusts and living sexually pure lives is essential to anyone who professes to know Christ. In doing so, we honor God with our bodies (1 Corinthians 6:18–20).
We know God’s rules and discipline reflect His love for us. Following what He says can only help us during our time on earth. By maintaining sexual purity before marriage, we avoid past emotional entanglements that may negatively affect present relationships and marriages. Further by keeping the marriage bed pure (Hebrews 13:4), we can experience unreserved love for our mates, which is surpassed only by God’s enormous love for us.
 Got Questions Ministries. (2010). Got Questions? Bible Questions Answered. Bellingham, WA: Logos Bible Software.