The Bible clearly condemns sexual sins: adultery (consensual sex between a married person and someone other than his or her spouse) (Proverbs 6:32; cf. 1 Corinthians 6:18 and Hebrews 13:4) and fornication (sexual immorality in general) are specified (Matthew 15:19; Romans 1:29; 1 Corinthians 5:1). Sex before marriage, or premarital sex, is not addressed in that exact term, but it does fall within the scope of sexual immorality.
The Bible teaches that sex before marriage is immoral in a couple of different passages. One is 1 Corinthians 7:2, which says, “But since sexual immorality is occurring, each man should have sexual relations with his own wife, and each woman with her own husband.” In this verse, marriage is presented as the “cure” for sexual immorality. Sexual union within marriage, which is commended, is set against immorality, which is to be avoided. Thus, any sex outside of marriage is considered immoral. This would have to include premarital sex.
Another verse that presents sex before marriage as immoral is Hebrews 13:4, “Marriage should be honored by all, and the marriage bed kept pure, for God will judge the adulterer and all the sexually immoral.” Here, we have both adultery and fornication contrasted with what happens in the marriage bed. Marriage (and sexual intercourse within marriage) is honorable; all other types of sexual activity are condemned as immoral and bring God’s judgment.
Based on these passages, a biblical definition of sexual immorality would have to include sex before marriage. That means that all the Bible verses that condemn sexual immorality in general also condemn sex before marriage. These include Acts 15:20; 1 Corinthians 5:1; 6:13, 18; 10:8; 2 Corinthians 12:21; Galatians 5:19; Ephesians 5:3; Colossians 3:5; 1 Thessalonians 4:3; Jude 1:7; and Revelation 21:8.
God designed sex, and the Bible honors marriage. Part of honoring marriage is the Bible’s promotion of complete abstinence before marriage. When two unmarried people engage in sexual intercourse, they are defiling God’s good gift of sex. Before marriage, a couple has no binding union, and they’ve entered no sacred covenant; without the marriage vows, they have no right to exploit the culmination of such vows.
Too often, we focus on the “recreation” aspect of sex without recognizing that there is another aspect—procreation. Sex within marriage is pleasurable, and God designed it that way. God wants men and women to enjoy sexual activity within the confines of marriage. Song of Solomon 4 and several other Bible passages (such as Proverbs 5:19) describe the pleasure of sex. However, God’s intent for sex includes producing children. Thus, for a couple to engage in sex before marriage is doubly wrong—they are enjoying pleasures not intended for them, and they are taking a chance of creating a human life outside of the family structure God intended for every child.
While practicality does not determine right from wrong, following the Bible’s instructions concerning sex before marriage would greatly benefit society. If the Bible’s message on sex before marriage were obeyed, there would be far fewer sexually transmitted diseases, far fewer abortions, far fewer unwed mothers and unwanted pregnancies, and far fewer children growing up without both parents in their lives. Abstinence saves lives, protects babies, gives sexual relations their proper value, and, most importantly, honors God. Sex between a husband and wife is the only form of sexual relations of which God approves.