My brother… left home to start living with his girlfriend. I have told him that he should get married because having sexual relations outside of marriage is fornication, but he says that… if a document alone constitutes a marriage, why didn’t God make Adam and Eve sign a document? Besides, he prayed for God to bless their union, and since he is having sexual relations only with his girlfriend, that makes her his wife.
Your brother’s question regarding Adam and Eve requires context to answer, for they aren’t the only ones who lacked a signed marriage contract. Many cultures and governments have had marriage agreements that have not required signing documents either.
In most of the world, marriages have traditionally been arranged between the parents of the man and woman. These agreements have been designed to bring families together and make alliances. When parents arranged a marriage, they would decide how much property the wife was to bring into the partnership. When the property was exchanged successfully, the couple was considered to be married.
However, marriage agreements were not the only kinds of ancient contracts that were carried out without documents. For example, in the book of Ruth in the Bible, we find that contracts were carried out in front of witnesses at the city gate, and one or both of the parties had to take off a sandal and offer it to the other party as a sign of agreement. (1)
Throughout history, piles of stones and engraved stones have symbolized agreements both between different people groups and between God and man. It could be said that this custom is the precursor of the wedding ring that has a gemstone in it. The ring is a public acknowledgement of the marriage agreement.
What all of these examples have in common is that each of them is a public agreement made in front of witnesses. The witnesses are the proof that both the man and the woman agreed to the marriage arrangement, and that neither was forced into the relationship.
In modern times, every country has legal requirements specifying the number of witnesses and the responsibilities of the man and the woman who are joining together. The document is just a modern way of setting up piles of stones or exchanging property.
The Apostle Paul wrote that we should obey the government, for God is the One who put it in place. (2) Therefore, followers of His Son Jesus Christ should make agreements in the way that their government prescribes, unless that method is contrary to Scripture.
Jesus said that the man and the woman who are united in marriage become one flesh, and that it is God who joins them together. (3) Your brother’s private prayer to God and his private agreement with his girlfriend do not fulfill the requirement of having witnesses, nor do they follow the legal requirements for marriage. No matter how sincere his prayer was and how convinced he is of his opinion, his arrangement is not marriage in the eyes of God.
We wish you well,
1 Ru 4:7,8
2 Ro 13:1
3 Mk 10:8-9