Society is rapidly accepting this idea, but what does God think? According to the Bible, a man and a woman living together unmarried are classified as 'living in fornication.' Fornication is a broad word meaning, 'every kind of unlawful sexual intercourse.' A couple engaged in sexual unions is either married or sinning; there is no middle ground. The Bible says, '... to avoid fornication, let each man have his own wife, and let each woman have her own husband' (1 Corinthians 7:2). One must cease fornication and be forgiven of it in order to go to heaven (Revelation 21:8; 1 Corinthians 6:9).
Since God instituted marriage in the first place (Genesis 2:24), this question is not merely cultural. The Bible gives no set ceremony as to what must be said or done as one enters a marriage; every culture is free to set up a system to recognize a couple has become husband and wife. In our country the law says that a couple must obtain a license and appear before one recognized by the state as authorized to perform marriage ceremonies. Each entering marriage must comply with the law of God and with the laws of the land (1 Peter 2:13-15; Romans 13:1-2). If the state does not accept a marriage without a license and ceremony, then neither does God. We might also point out that there are 'marriages' that the state recognizes that God will not (Matthew 19:9; Romans 7:1-4).
Jesus said to the Samaritan woman at the well, 'thou hast had five husbands; and he whom thou now hast is not thy husband' (John 4:18). She had met the requirements of the state five times, but not the sixth. This teaches that we must comply with the laws of the land and that mere cohabitation does not constitute a marriage. If sexual union makes a marriage, then Jesus erred in saying, 'He whom thou now hast is not thy husband.' If sexual union makes a marriage, then everyone who employs the services of a prostitute is married to her. God must join two together for them to be married. Jesus said, 'Wherefore they are no more twain, but one flesh. What therefore God hath joined together, let not man put asunder' (Matthew 19:6). God only joins those who meet His requirements.