I took part in a lively discussion at the Dalrock blog discussing what signifies the start of a biblical marriage. The traditional Christian viewpoint is that it begins with a marriage ceremony. Historically this was marriage by a member of the clergy, although civil marriage is given equal weight by most. Only a small minority took the sex=marriage viewpoint.
The discussion was precipitated by the non-traditional views of Artisanal Toad, a polygamist that I have debated with in the past. He holds a variety of unusual viewpoints. Among them are the view that marriage begins with the first sexual act. There are some eligibility requirements that have to be met, but he rejects the notion that a marriage ceremony has any significance at all.
Much difficultly comes with meaning of the word ‘marriage.’ When the word is used in the Bible, it is used in three different ways: Marriage beginning with the sexual act in the absence of a ceremony, marriage beginning with a ceremony or agreement absent the sexual act, and marriage beginning with both.
This creates difficulty for both the ceremony=marriage and the sex=marriage views. Each of these viewpoints attempts to minimize the evidence in favor of the other viewpoint, trying to rationalize it away. I was dissatisfied with either approach because it was unable to cleanly harmonize the complete biblical teachings on the subject.
The fundamentals of marriage are described right away in Genesis 2:18-25.
The reason given there for marriage is that man and woman were meant, by design, to be together. This mirrors the relationship between God and man. We were meant, created in fact, to be in a relationship with God. This makes marriage sacred.
At least as important is a husband and wife becoming one flesh. What does this mean? Below we’ll examine Jesus’ teaching, but first let’s look at the various meanings attributed to this terminology.
First, becoming one flesh is metaphorical. They become completely united in purpose and should no longer be thought of strictly as individuals. A husband should see the wife as an extension of himself, and she should do the same of him. Neither should ever think solely of themselves. To marry is to give up sole control of one’s self.
Second, there is a spiritual joining that transcends the physical. The pair are joined together with a spiritual bond and become inseparable. This, again, mirrors the relationship with God, a bond that is intended to be permanent.
Third, it refers to the creation of children. Literally by joining their flesh together, they gain the power of creation, the very power that is described in Genesis 2. Genesis never says that creation ended, only that God rested on the seventh day. This is our sacred inheritance: to take the baton, as it were, of creation and continue it in the form of procreation.
Fourth, it refers to the joining of blood, that is, family. When the pair are married, their families become one family. This is why a man could not marry his deceased wife’s sister: it was considered incest, even though they did not literally share the same genetics.
Fifth, and this is the hotly debated point, becoming one flesh refers to having sex for the first time. Here I take the non-traditional, minority viewpoint and note that because no ceremony is mentioned here, this refers to having sex as the beginning of the first marriage. The contextual and linguistic evidence strongly supports this conclusion.
Sixth, whether the joining into one flesh is physical, metaphorical, or spiritual, the word for the pair being united is more like glue. They are stuck together (pun intended). The implication is permanence.
Now we must look at the words of Jesus in Mark 10:1-12. The Pharisees asked Jesus a technical question on the Law regarding divorce. Jesus replied by quoting Genesis. He stated that God created humans specifically as man and woman, that they are intended to become one flesh, and that this bond is permanent and cannot be set aside by man. He then declares that this is why divorce and remarriage constitutes adultery.
Jesus understood divorce to be the opposite of the one-flesh joining, that is, sex. The logic is simple. The divorce, a human institution that cancels marriage, cannot set aside the one-flesh bond that God has set. Divorce or not, marriage or not, sex with the other woman is adultery. The one-flesh bond is permanent and unbreakable except through death.
The key to the original riddle is to understand marriage as a social construct and marriage as God views it: a one-flesh joining. These two concepts are so intertwined in the Bible, that it’s almost impossible to separate them. And they really shouldn’t be. Sex is a one-flesh joining, even in the absence of the social construct called marriage. This is seen most clearly in 1 Cor. 6:16-17 where sex with a prostitute constitutes a one-flesh joining. Yet sex and marriage belong together. It is always an aberration when they are separate. Sex is what makes a ‘marriage’ indissoluble.
Regardless of whether or not there is a marriage, sex creates a one-flesh joining. This may be licit or illicit. The only time it is licit is in the context of a new or existing marriage. Thus, all sex outside the bounds of marriage is unconditionally wrong. To put it more technically, sex always creates an implied obligation or expectation of a marriage. Adultery violates the core tenants of marriage because the one-flesh joining creates an implied promise that cannot be fulfilled.
Marriage is more than just sex or a ceremony. Trying to reduce it to just one of these things misses the depth and importance of marriage. It is just another way of minimizing the importance of marriage in the eyes of God. We must not do this. Marriage and sex are fundamental to creation. They are God’s final work of creation in Genesis. We would do well to treat them with the utmost respect that they deserve.
 Or related terms. For example, ‘husband’ and ‘wife’, which obviously imply marriage, are used in similarly ambiguous fashion.
 Genesis 2:23 is poetry. It describes the splitting of a man to create a woman. In v24 it describes the rejoining that occurs in sex. It is a point, counter-point.
 No-fault divorce stands in stark contrast to the sacredness of marriage.
 See 1 Cor. 6:16-17.
 This is one of the primary reasons abortion is wrong. Aborting a baby is the antithesis of Creation. It violates the fundamental order of creation. It is one reason why the Roman Catholic Church stands so strongly against birth control, especially chemical birth controls that prevent implantation or end a pregnancy after conception.
 See What is the Torah?.
 The sex=marriage and ceremony=marriage viewpoints both miss the point. Both are correct and wrong at the same time.
 This of course includes sexless marriages. David and Abishag did not consummate their marriage and it created a serious political problem because they were not one-flesh joined.
 Sex that creates a marriage, such as that between two unmarried virgins, is licit, so long as it results in a marriage in actual fact. Premarital sex can only be resolved by becoming officially married or remaining unmarried for the rest of their lives.