Marriage, like love and procreation, is a life enhancement created by our heavenly Father. He made Eve to complete the creation of man, brought her to Adam, and joined them as husband and wife. The unconditional union of a man and a woman in marriage for as long as they both live is his design (Genesis 2:24). It has his approval and blessing (Genesis 1:27-31).
Among the blessings that our loving Father intends for married couples are companionship, sexual happiness, chastity, and children (Proverbs 18:22, Hebrews 13:4, Psalm 127:3).
In addition, he protects and cares for marriage in a variety of ways—not only by treating it as a lifelong union, but by forbidding sexual activity outside of this bond and by clarifying the role relationships of a husband and his wife.
His design for marriage is that a husband love his wife and sacrifice himself for her, motivated by the love that Christ has shown for both of them (Ephesians 5:25-28, 1 Peter 3:7). His plan also is that a wife love and respect her husband in the same way that she shows her love for Christ (Ephesians 5:22-24, also see Ephesians 5:33). If a marriage relationship is blessed with children, he intends that fathers take a leading role in bringing up their children as Christians (Ephesians 6:4).
Our present marriage laws recognize public, present consent, not cohabitation, as that which establishes marriage. This reflects what Scripture says also. Most cohabitating couples in the United States do not regard or refer to each other as husband and wife and are not legally married no matter how long they live together.
Even though our unbelieving society embraces living together outside of marriage as an acceptable lifestyle, it is still a sinful arrangement. A pastor or congregation will deal patiently with cohabitating people who are seeking spiritual guidance or if they are new Christians who are just beginning to grow in their Christian life of sanctification. This is done by firmly yet gently confronting them with their sin, comforting them with the joy of forgiveness and eternal life through Christ, and then guiding them to change their behavior to show their love for Christ.