Why does God prohibit sex outside of marriage?
Is there any reason other than as Creator He gets to set the rules? —James
God has written sexuality into the world’s narrative for many reasons. Procreation, partnership, and pleasure are among the most commonly noted. Restricting sex to marriage, however, does appear arbitrary if these are the only reasons.
A “thick reading” of Scripture on human sexuality reveals that God’s restriction is not arbitrary but follows from sex’s function as a profound metaphor for Christ’s union with His Church and, ultimately, the inner life of the Trinity.
First, sex was God’s idea, not man’s. It was part of God’s “very good” original Creation (Gen. 1:31; 2:24). It is not a “lower” or “baser” part of humanity. It certainly is not an animalistic remnant of humanity’s falsely-alleged evolution. God declares it honorable (Heb. 13:4), and He requires sexual union in marriage where possible (1 Cor. 7:3-5).
The Holy Spirit commands men to be “intoxicated” with the wife of their youth, and forbids them to be “intoxicated” with the bosom of an adulteress (Prov. 5:19-20). Scripture does not blush to extol the potential joys of sex within marriage, though it is realistic about the challenge our fallenness creates for realizing those joys (Song of Solomon).
Second, sex involves Christ. 1 Corinthians 6:13 tells us that God gave humans bodies “not for immorality, but for the Lord, and the Lord is for the body.” God planned from eternity to make our bodies His temple (1 Cor. 6:19) and to unite us with Christ in such a way that what we do with our bodies involves Christ. This includes sex.
As unthinkable as it may seem, Paul says that if a believer is joined to a prostitute, he has joined Christ to the prostitute (1 Cor. 6:15-16). Since we are members of Christ’s body, whatever we do with our bodies implicates Christ. If it is true that joining to a harlot would join Christ to her, it is necessarily true that becoming one flesh with one’s spouse joins Christ to him/her as well.
Christ is present in us by His Spirit and partakes in all we do. Consider the horror of pornography! This is why all that we do with our bodies must glorify God; that is, it must reflect the unique excellence of His character (1 Cor. 6:20).
Third, sex pictures Christ’s union with His bride. In Eph. 5:31, Paul quotes Genesis 2:24 regarding sexual union in marriage: “a man shall…be joined to his wife and the two shall become one flesh.” One flesh union is itself mysterious. Paul takes us deeper: “This mystery is great; but I am speaking with reference to Christ and the Church” (Eph. 5:32).
God created sexual union to teach us about spiritual union. Marital union is a picture prophecy of Christ’s union with the Church. Christ takes her to himself only through a covenant (Heb. 9:15). Christ enters His bride and indwells her (Col. 1:27). Christ is also indwelt by her (John 15:5).
Christ takes only one wife to whom He commits himself eternally (Rev. 19:6-9). Sex is God’s amazing metaphor to picture this relationship of covenantal fidelity, mutual indwelling, other-serving, self-sacrificing love. Sex outside of marriage portrays Christ as unwilling to sacrifice Himself to sanctify another, unwilling to covenant to exclusive faithfulness, unwilling to seek the other’s best interest, but seeking His own pleasure at others’ expense.
God forbid! Any sexual union outside of heterosexual monogamy misrepresents—indeed, blasphemes—the ultimate union toward which all sex was intended to point, the union of Christ and His Bride.
Fourth, sex reflects God’s triune inner life. God the Father, Son, and Spirit mutually indwell one another in transparent, face-to-face,
covenantally committed, self-giving, loving delight (John 14:10; 17:21).
Divine love overflows in Creation and new creation, bringing persons into being to share His joyous family life. Now God’s image bearers extend Creation in procreation, for married sexual love brings persons into being to share in a joyous family life.
Sex outside of marriage portrays God as a hedonistic, feckless, even absentee father. No wonder God forbids it!