The Bible says that marriage happens when “a man leaves his father and mother and is united to his wife, and they become one flesh” (Genesis 2:24). It is the “one flesh” aspect of marriage that has led some people to assume that, if an unmarried couple has sex, then they are married in God’s eyes. Is it as simple as that? Or is there more to marriage than the physical act of sex?
We do not believe that the act of sex alone constitutes marriage. We have three reasons for saying so.
First, a reason based on logic. If it were true that premarital sex makes a couple married in God’s eyes, then there would be no such thing as premarital sex. The instant an unmarried couple have sex, they would lose their “premarital” status, becoming each other’s de facto spouse. The Bible’s warnings against premarital sex—a type of fornication—would thus be rendered irrelevant. Premarital sex could not be considered immoral because, the moment sexual intercourse occurred, it would become marital sex. To avoid immorality, couples are counseled in 1 Corinthians 7:2 to get married; but if sex equals marriage, the counsel simply becomes, “To avoid immorality, have sex.” And that’s not the advice Paul was trying to give.
A second reason that the act of sex alone does not constitute marriage is based on the meaning and significance of marriage. The biblical picture of marriage involves the union of a man and woman in every way possible: mentally, emotionally, morally, spiritually, economically, and, yes, physically. Sex joins a man and woman physically and to some extent emotionally, but there is no other union that results. To reduce marriage to the physical union of two people is to disrespect God’s design and ignore most of what marriage is.
Third, marriage requires commitment, and sex does not. In fact, sex cannot provide a sufficient basis for establishing an ongoing relationship. The 1994 movie Speed closes with the two main characters, Jack and Annie, embracing. Jack tells Annie, “I have to warn you, I’ve heard relationships based on intense experiences never work,” to which Annie replies, “OK. We’ll have to base it on sex then.” And they kiss, and the credits roll. Such dialogue is comically fictitious and only works in Hollywood. Committed relationships are grounded in the union of will and intellect and material resources. That’s why cultures worldwide have developed accepted ways of formalizing the marital relationship to make it socially and legally binding.
If an unmarried couple has sex, does that mean they are married? No. The idea is foreign to the Bible, in which premarital sex is considered the sin of fornication. Sexual intercourse may have joined the couple physically for a moment, but that is quite different from God joining them together as husband and wife. It could be that premarital sex will lead to a “shotgun wedding” and a ceremony that “makes an honest man” of the groom. But it’s the ceremony that ties the knot, not the act of sex.
Sex is an important aspect of marriage according to God’s design of intertwining a man and a woman in a committed, lifelong relationship. Sex between unmarried people, though it mimics the physical act of marriage, does not equal marriage.