From the beginning of the human race, God has proclaimed the concept of union through the relationship of a man and woman. "And Adam said: "This is now bone of my bones and flesh of my flesh; she shall be called Woman, because she was taken out of Man." Therefore a man shall leave his father and mother and be joined to his wife, and they shall become one flesh" (Genesis 2:23-24). Here in the very first marriage nothing is said about a covenant or ceremony or vows, but we find an amazing statement of union. The two (man and woman) became one in God's eyes. I believe this statement by God should form the foundation for how we think about marriage.
In the Ephesians 5 passage quoted at the beginning, Paul speaks about the marriage relationship and the union of Christ with the church with exactly the same words used in Genesis. Paul says we are members of Christ, of His flesh and of His bones. The relationship is comparable, and both may be referred to as a mystery. I believe we must see the connection between these two in the mind of God as we think about either relationship.
The significance of this may not be obvious at first, but I believe it will become more so as we continue. In the marriage relationship God holds a picture before us at all times, of the relationship that exists between His bride (the church) and Himself. The example is first for the man and woman, then for the children, but also for all of mankind as they look on. The heavenly relationship goes beyond the earthly relationship, but both cooperate to reveal the mind of God to us. His thought in both is union. If we accept a lower idea about either relationship, our concept of the other will suffer as well.
What are some of the usual concepts about what creates the marriage relationship? Some would say marriage is primarily a covenant: that the relationship is established as two people commit to each other in a binding covenant before God. A husband and wife are admonished not to break the covenant, or may be taught that before God it cannot be broken except by death. While I agree that both should have this covenant commitment in their hearts as they enter into marriage, the flesh is weak and the reality is that one or both may break the covenant.
Consider these words of Jesus: "And He answered and said to them, ‘Have you not read that He who made them at 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 then, they are no longer two but one flesh. Therefore what God has joined together, let not man separate'" (Matthew 19:4-6). What does this passage say makes two one? Is it a covenant? A ceremony? Vows in a public setting? The scripture does not say so. Rather it says that there is a "leaving" and a "cleaving." Then Jesus says: "What God has joined, let not man separate." The union made by God based on the couple's actions cannot be broken. Man may choose to break a covenant, but only death can break the union that was created by God. This is the only definition of marriage that I can find in the scriptures. I believe there will be a binding covenant in the hearts of those who enter into marriage seriously before God, and this is right and good, but again, it is the act of God which makes them one, as seen in Malachi 2:14-15: "…Yet she is your companion and your wife by covenant. But did He not make them one, having a remnant of the Spirit? And why one? He seeks godly offspring…"
What does it mean to "leave and cleave"? My own answer is that a man openly leaves his father's house (authority) and joins himself to his wife as they set up another household. It is not a secret thing, but something done before men and God. They live openly as husband and wife. Based on this, God declares them one. It is not what they say that makes them one in God's eyes, but what they do.
With the looseness of relationships in our day, a frequent question that arises is: when is this marriage "authentic" in God's eyes? Men have struggled over this question for centuries and tried to make rules to cover every situation. Personally, I doubt that we can come up with rules that answer every question. For a normal wedding where the announcement is made at a public ceremony and the marriage consummated through physical union, I think the answer is clear. But if a couple sets up a household privately, we may have questions. If this is the case, I can only encourage a couple that is serious with God to go to Him for the answer. He is the One we will stand before someday, and I believe He will be faithful to answer an honest heart. Remember, He is for us, not against us.
Many (or perhaps most) would say that the social law of their country determines whether a couple is married or not. By this concept, even if two live openly as a couple, if they do not follow the laws of the land and execute a marriage license (or whatever is customary), they are not married and are not one in God's eyes. Those who hold this view would say that the couple is living in fornication during this time. But I would ask: where do we see man's laws in the Genesis account? Where do we see them in the story of Isaac and Rebecca? Were these two not married (one) in God's eyes? After a couple lives together for a period of time, even most governments recognize this as a "common law" marriage.
I am not making a case for ignoring the laws of the land, for we are admonished to keep them for testimony's sake. But I do not see a basis in scripture to say that obeying the laws of the land is what makes a couple one in God's eyes. What I do see is that if a man and woman "leave and cleave," God says they are one, whether they obey the laws or not. Obeying the laws makes the marriage clear in man's eyes and gives a good testimony, but it does not make them more "one." God is the one who joins, not man. In addition to this, the danger I see in this view is that it opens the door for man to separate the couple. In other words, "What man has joined, he may dissolve."
Another group would say it is the church that joins a couple. Some religious groups go so far as to say that the only marriages God recognizes are the ones their group performs, and all the rest of the world is living in sin. There are many variations of this viewpoint, but where do we see any example or teaching in scripture that gives the church (or any religious group) authority to make a man and woman one in God's eyes? I cannot find it. Again, if a religious group had the authority to make a couple one, it would open the door for them also to dissolve the relationship.
I believe it is extremely important to see that the union created when a couple "leaves and cleaves" is the foundation of a marriage. Union is what makes a man and woman married in God's eyes, and only death can break this union. "Or do you not know, brethren (for I speak to those who know the law), that the law has dominion over a man as long as he lives? For the woman who has a husband is bound by the law to her husband as long as he lives. But if the husband dies, she is released from the law of her husband" (Romans 7:1-2). "A wife is bound by law as long as her husband lives; but if her husband dies, she is at liberty to be married to whom she wishes, only in the Lord" (1 Corinthians 7:39).