what does the bible say?
God created sex as a beautiful gift for a husband and wife to enjoy within marriage. His purpose for this gift was to provide His creation with a human experience that would represent His spiritual relationship with them. Ephesians 5:31–32, quoting from Genesis 2:24, explains, "'Therefore a man shall leave his father and mother and hold fast to his wife, and the two shall become one flesh.' This mystery is profound, and I am saying that it refers to Christ and the church." The image of marriage points to God’s relationship with His people. It is also the building block of society. Thus God takes marriage, and sex, very seriously (1 Corinthians 6:15–20; Hebrews 13:4).
Sex is God’s established means of procreation for humanity to “be fruitful and multiply and fill the earth and subdue it” (Genesis 1:28; cf. Genesis 9:2). But sex is not merely a means to an end, and children are not merely earth fillers. Sex is the way in which new humans—who bear the image of God (Genesis 1:27)—are conceived and formed in the womb (Psalm 139). This fact alone makes sex meaningful. But sex is not only about procreation; it is intended for married couples for a variety of reasons beyond producing offspring.
Sex is a unique form of intimacy and knowing that points to the deep knowing and intimacy God’s people have with Him. The context of a one-man-one-woman covenantal marriage is intended as a protected space for this deep level of vulnerability and trust. Fully committed, husband and wife are free to give of themselves to one another—not for self-fulfillment, but for the benefit of the other. When both are giving in this way, they both experience agape love and the joys of being giver and receiver. With Christ, we can be fully known and vulnerable because His promise to us is unbreakable. He is the ultimate display of self-sacrificial love, giving Himself fully so that we might have relationship with God (Philippians 2:1–11; Hebrews 12:1–2). In addition, husband and wife bring one another pleasure as they give of themselves in sex. This is a good gift from God for which to be grateful.
As stated, all of this is designed for one man and one woman in the covenant of marriage. Outside the boundaries of marriage, sex is a sin. This includes sex before marriage.