God created man as male and female (Gen 1:27) with the capacity for sexuality, properly taking place only between a husband and a wife (Gen 2:24; Heb 13:4) for the purposes of procreation (Gen 1:28; 9:1) and relational enjoyment (Gen 2:18, 24). In a fallen world, sex in marriage helps to restrain temptation to sexual sin (1 Cor 7:2, 5).
As Christians, we must remember that our bodies belong to the Lord, are members of Christ, and are temples of the Holy Spirit, having been bought with the blood of Christ (1 Cor 6:13, 15, 19–20; 1 Thess 4:7–8; cf. 1 Pet 1:18–19). It is God’s will for us to control our bodies in holiness and honor (1 Thess 4:3–4). When Christ returns, our bodies will be changed to be like the Lord Jesus Christ’s body, perfect and incapable of sin (1 Cor 15:51–58; Phil 3:21; 1 John 3:2).
Unbelievers reject God’s truth, however, and live according to the impure lusts of their hearts, leading to dishonorable actions with their bodies, to one degree or another (Rom 1:18–20, 24; 1 Thess 4:5).
Lust itself is sin, that is, the willful longing for sex outside of marriage. This lust can take place by looking at someone with lustful intent (Matt 5:28; cf. Jas 1:14–15). This lust can be provoked by pornography, which is itself immoral in its production and various forms of media.
Unchecked lust leads to acts of immorality (any form of sex outside of marriage), which are against the will of God (1 Thess 4:3; cf. 1 Cor 6:18; 2 Cor 12:21; Gal 5:19; Eph 5:3; Col 3:5). These acts include fornication (premarital sex) and adultery (extramarital sex).
Homosexuality is another perversion of sex expressly forbidden in Scripture (Lev 18:22; 20:13). It is contrary to sound doctrine and not in accordance with the gospel (1 Tim 1:10–11). Homosexual sex between men or women stems from dishonorable, sinful passions and is a shameless act that abandons natural sexual relations between a husband and a wife (Rom 1:26–27; e.g., Gen 19:5, 7; cf. 2 Pet 2:7; Jude 7). God punishes this sin by giving the sinner over to the sin itself and its various consequences (Rom 1:27), including exclusion from the kingdom of God (1 Cor 6:9–10).
Other sexual sins are so sinful that even unbelievers condemn them, including rape (e.g., 2 Sam 13:14), incest (Lev 18:6–18; 1 Cor 5:1; e.g., Gen 35:22), and bestiality (Lev 18:15; 20:15–16; Exod 22:19).
In the Old Testament, the nation Israel was to administrate severe punishment for various sexual sins according to Mosaic Law (e.g., Lev 20:10–16). In our age, God commands exclusion of the unrepentant, immoral person from the church (cf. Matt 18:15–17; 1 Cor 5:1–11), and, in the end, the unrepentant will not inherit the kingdom of God but will be forever consigned to the lake of fire (1 Cor 6:9–10; Rev 21:8). However, the repentant sinner who finds forgiveness in Christ can see himself in these words: “And such were some of you. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God” (1 Cor 6:11).1
- Three sources helpful to me for this post were the relevant chapters in John S. Feinberg and Paul D. Feinberg, Ethics for a Brave New World (2nd ed.; Wheaton, IL: Crossway, 2010); Norman L. Geisler, Christian Ethics: Contemporary Issues and Options (Grand Rapids, MI: Baker Academic, 2010); and Andreas J. Köstenberger and David W. Jones, God, Marriage, and Family: Rebuilding the Biblical Foundation (2nd ed.; Wheaton, IL: Crossway, 2010).