(I was asked to post on Deily's new "Ask an Expert" segment on Patheos. My assigned question: Where in the Bible does it say sex should be restricted to marriage?) “Marriage should be honored by all, and the marriage bed kept pure,” we read in Hebrews 13:4, “for God will judge the adulterer and all the sexually immoral.” As the Ashley Madison scandal shows, it’s easy to find agreement that adultery is wrong because it breaks vows made in a wedding ceremony. But what about sexual activity between consenting adults independent of any wedding promises? Few in our culture would advise against this. But the writer of Hebrews 13:4 does. If the only way marriage was “honored by all” was by avoiding adultery, the biblical writer would not have added a warning against “all the sexually immoral.” Whenever we engage in sexual activity that is separated from marriage we fall short of God’s standards. The reason for this is not because the biblical writers had a low regard for sex, but a lofty one. Butch Hancock of the Flatlanders band once joked about growing up in the religion-saturated Texas panhandle. “Life in Lubbock, Texas, taught me that sex is the most awful, filthy thing on earth and you should save it for someone you love.” It’s a funny line, but either he didn’t spend any time in biblically-formed congregations, or he didn’t understand what they were trying to tell him. After all, in the Bible we find the encouragement for a young husband to find delight in his wife’s breasts “always” (Proverbs 5:18-19), we find the comparison of a honeymoon night to a lavish feast (Song of Solomon 5:1), and we find instruction to both husband and wife to mutually meet each other’s sexual needs (1 Corinthians 7:3-5). But why limit such a wonderful experience to a husband and wife within marriage? Marriage is a contract, or—better—a covenant. In the wedding ceremony, we publically commit ourselves to the well-being of the other. Sex then reflects this bond of marriage. In the first mention of sex and marriage in the Bible, we are told that “the two will become one flesh” (Genesis 2:24). One flesh: That means coitus, right? Yes, but more. When we say we have an “eye” for someone, that’s a synecdoche, a figure of speech where a part represents the whole. In the Bible, “flesh” is often a synecdoche. When we read in Genesis 6:12 that “all flesh” had become corrupt that means more than only bodies were sinning. When we read in Joel 2:28 that God would pour out his spirit on “all flesh,” that that means more than only bodies would benefit from the divine experience of the Spirit. And when we read in Genesis 2:24 that in sex two become “one flesh,” that means more than only bodies are united. We understand this even if we’ve never read a Bible. Sex has emotional and relational elements to it that go beyond the mere satisfaction of genital stimulation. Even when bodies join together outside the confines of marriage, it provokes feelings of loyalty, safety, and sensitivity. That’s why we’re out of sorts if the other person doesn’t call after spending a night with us. We have to work hard to persuade ourselves that we’re okay with that, because such dismissal of our affection sure doesn’t feel natural. I’m reminded of that line from the woman who was stalking Tom Cruise’s character in the movie Vanilla Sky. “Don’t you know,” she said, “that when you sleep with someone, your body makes a promise whether you do or not?” Because we have these feelings toward another person after we’ve joined our body with theirs, we can relate to Paul’s argument in 1 Corinthians 6:16. “Do you not know that he who unites himself with a prostitute is one with her in body?” he asks, adding for explanation, “For it is said, ‘The two will become one flesh.’” Of course, even those who do not take the Bible as their guide would agree that visiting prostitutes isn’t ideal, to say the least. But note the basis of Paul’s argument. He does not say, “Don’t visit a prostitute because it’s potentially unhealthy, possibly dangerous, and you may get ensnared in scandal.” Instead, he says, “Listen, don’t you know that in sex you become one with another person—physically, emotionally, in every way? If that’s not what you’re looking for with a prostitute, don’t have sex with her.” But many would say that is what they are really looking for when they undress with someone they’re fond of. They hope that the sexual union will lead to relational union, and all the benefits that come from it. Sadly, this doesn’t always happen when the sexual union comes before the covenant. In his book, Premarital Sex in America, University of Texas sociologist Mark Regnerus wrote, “The sooner relationships become sexual, the greater their odds of failure. This is not to suggest that all such relationships will fail – just that they’re more apt to. Relationships started with sex are even more tenuous. No shortage of emerging adults, however, think the data must somehow be wrong. Hence, they act like it’s not true, only to become part of the same data pattern themselves.” The wisdom of the Bible is worth returning to as a culture. Couples should first enter a covenant with each other and then engage in the act meant to reflect such a covenant.