In today's world of controversy surrounding ideas such as homosexual "marriage," there is a general push to redefine marriage so as to suit present cultural desires. It is common for people to argue that there is not, in fact, one biblical definition of marriage. The Bible, it is claimed, institutes a broad range of entirely different definitions of marriage at various times. Such statements typically involve ripping out a handful of Old Testament laws related to marriage and inheritance in the Levitical code and presenting them as if they offered wholly distinct definitions for the word. The reality is, however, that the Bible has one and only one definition of marriage, which it utilizes from beginning to end. Though different regulations are employed at various points in the biblical narrative, the institution itself remains the same essential thing.
The Biblical Definition
Marriage is central to biblical sexual morality, and so it makes sense that the Bible establishes marriage at the very beginning. In Genesis 2, God creates man. God declares that it is not good for man to be alone and forms a suitable mate for him out of one of the man's own ribs so that both the man and the woman came literally from the same flesh and bone. They were two separate people from one body. The text then states:
"For this reason, a man shall leave his father and his mother, and be joined to his wife; and they shall become one flesh" (Genesis 2:24).
Here we have a man and woman leaving their parents (who are also a man and a woman) and creating a new household together through a permanent joining, the two becoming "one flesh." Jesus himself points back to this as the beginning of an enduring and unchanging definition of marriage:
"And He answered and said, 'Have you not read that He who created them from the beginning made them male and female, and said, 'For this reason a man shall leave his father and mother and be joined to his wife, and the two shall become one flesh"? So they are no longer two, but one flesh. What therefore God has joined together, let no man separate” (Matthew 19:4-6).
Jesus then discusses certain Mosaic regulations regarding divorce that were temporarily given because of the hardness of people's hearts and He offers the proper perspective on how marriage ought to be lived out. Never is there a hint that this central definition was ever up for questioning. Marriage is a covenant that is both legal and relational, and that binds one man and one woman into a new family intended to be for life.
The Polygamy Question
The first and most forceful objection most people raise is the matter of polygamy. Doesn't the Old Testament allow men to take multiple wives? Or even if it doesn't outright condone it as proper, doesn't it at least describe it as marriage? Doesn't that show that the Bible was willing to accept polygamy as, even if not a moral ideal, still being a legitimate expression of marriage? Doesn't that mean that the Bible allows for more than one definition of marriage?
All of the moral considerations involved in polygamy, why it is wrong, and yet why the Bible frequently describes it occurring even among the heroes of the Old Testament are important and necessary topics. They do not, however, involve a discussion of a different definition of marriage. While at first glance polygamy seems to deny outright the idea that marriage is between "one man and one woman," the fact is that even Old Testament polygamy assumes this definition to be true!
Jacob may have married both Leah and Rachel, but Leah and Rachel were not married to each other! Polygamy was not one big marriage, but rather one man entering into more than one separate marriage at the same time. Jacob had one marriage with Rachel and another marriage with Leah, and each of these marriages was between one man and one woman. The sin of polygamy is not one of definition but of application. A man should not enter into more than one marriage at the same time. But even the men who did so understood that they were in more than one marriage. None of them thought that they and all their wives were all married to each other in one big, convoluted marriage. So even in the sin of polygamy, we still see the same definition of marriage assumed.
Levirate Marriage and Other Laws of Israel
The Levitical law requires marriage in a variety of scenarios that seem unusual and often quite distasteful to people today. They are situations in which our society would not expect the people involved to marry. But do these examples constitute a different definition of marriage?
The most common example is that of Levitate marriage:
"When brothers live together and one of them dies and has no son, the wife of the deceased shall not be married outside the family to a strange man. Her husband’s brother shall go into her and take her to himself as wife and perform the duty of a husband’s brother to her. It shall be that the firstborn whom she bears shall assume the name of his dead brother, so that his name will not be blotted out from Israel. But if the man does not desire to take his brother’s wife, then his brother’s wife shall go up to the gate to the elders and say, ‘My husband’s brother refuses to establish a name for his brother in Israel; he is not willing to perform the duty of a husband’s brother to me.’ Then the elders of his city shall summon him and speak to him. And if he persists and says, ‘I do not desire to take her,’ then his brother’s wife shall come to him in the sight of the elders, and pull his sandal off his foot and spit in his face; and she shall declare, ‘Thus it is done to the man who does not build up his brother’s house.’ In Israel his name shall be called, ‘The house of him whose sandal is removed’" (Deuteronomy 25:5-10).
Today, many people have a lot of trouble truly grasping the matters of family name, inheritance, household honor, and similar considerations involved in this scenario. It is a civil law deeply connected with the concerns of Old Testament Israel in the promised land given to them, not a universal law for all peoples at all times. Even here, though, is there anything that offers a new definition of marriage itself? The wife is still a woman. She is taking a new husband only because her former husband has died. Her former husband was a man. Her new husband is to be a "close brother," so by definition a man. We might balk at requiring these people to marry one another, but the marriage is, by definition, still the same concept of marriage. It is still one man and one woman entering a covenant bond and forming a household intended for life.
The same reasoning should be applied to the other Old Testament laws as well. They often require people to marry in situations that seem unusual to us, but when you ask what they mean by the word "marry" in any of these contexts, you come back to the very same definition of the word.
The Bible does, indeed, hold to only one definition of marriage, and while that definition certainly allows a certain variety of customs and legal applications in differing contexts, there are many things it plainly does not allow. Things like a man marrying another man, or a woman marrying another woman, and two men and three women all marrying each other in one big marriage, or a man marrying his goldfish, or a woman marrying the color blue. All of these things are incoherent and outside of the clear definition of marriage given by God in Scripture, and a Christian simply cannot support such a redefinition of what God instituted for all mankind from the very beginning.