Here are some Biblical reasons for marriage.  The first five would be true even if man had not sinned. Only the last two are a result of sin in some way, though of course sin affects our ability to fulfill the first five. These are not in any particular order. 

First, God ordained marriage for taking dominion over the earth. Genesis 1:26-28 gives us God’s original plan for man.  Man was given dominion over the earth, he was to fill the earth and subdue it.  Eve was to be Adam’s helper as he subdued the earth (Genesis 2:18). Psalm 8 makes it clear that this dominion still belongs to man even after the sin in the Garden of Eden. Christ redeems us so that we might participate in His taking dominion over the earth.  Of course, a single person can participate in the dominion mandate. But typically we fulfill this command through getting married and having children. 

Second, God ordained marriage to be a witness to Christ and his church. Churches love to talk about evangelism, which is of course a good thing. But marriage is explicitly called a picture of Christ and his church. Ephesians 5:22-33 makes it clear that when a man and woman get married they immediately become a living, breathing painting of Jesus and His Bride. This means our marriages always point to something greater than the marriage itself. A failed or bad Christian marriage is a slander of Jesus Christ.

Third, God ordained marriage for our companionship. It was not good for Adam to be alone.  Over the years we are married there should be an emotional and spiritual intimacy that develops between husband and wife. There is a lot of sentimentality that surrounds marriages. People talk of “soul mates” and such things.  As Christians we should avoid this. But there is a kernel of truth there. God does want us to grow closer to our spouse. Husbands and wives should enjoy each other’s company and companionship more and more over the years.   

Fourth, God ordained marriage for the bearing of children. This is explicitly stated in Genesis 1:28. The Scriptures see children of covenant parents as a great blessing to God and his Kingdom. The Scriptures assume and expect that godly marriages will be fruitful and bear many children (See Deut. 28:4, 11, Psalm 127-128, I Timothy 5:10, 14, Titus 2:4).  A couple that refuses to bear children is violating God’s Word. If a couple cannot have children that does not mean they are not blessed by God. God intends to bless that couple in other ways and for them to honor him in other ways. However, most Christian marriages should result in a having many children and bringing them up in the discipline and instruction of the Lord.

Fifth, God ordained marriage for our physical pleasure. Proverbs 5:15-20 and the Song of Solomon make this point. The sexual relationship is not just for the bearing of children or for sexual protection. It is also for the joy and pleasure of the couple. God intended for us to enjoy our spouses physically. Too many Christians find this a bit much, that God would create such a physical high. “Is that really spiritual”, we ask? But God made sex to be thoroughly enjoyed within marriage. It is not an idol to be worshiped. And your goal is not to have the “best orgasm in history” as the world tells us. But the marriage bed is meant to be fun and exciting. Those who tell you otherwise are liars. 

Sixth, God ordained marriage for our sexual protection. Paul makes this clear in I Corinthians 7:2-5. Getting married is one of the ways God keeps us from burning with lust. Long delays in getting married, which are common in our culture, make us more vulnerable to sexual sin including pornography and fornication. Marriage is not an automatic cure for sexual sin, but it does help. 

Seventh, God ordained marriage for our sanctification.  There are few situations like marriage and raising children that can show someone their sinful heart. We get married believing we are great and wonderful, only to find out there are a lot of ungodly thoughts and emotions that we need to repent of. Later we think we matured spiritually then children come along and the process starts all over again. God sanctifies us in other ways. But marriage is  one of the primary ways he helps us grow in the image of Christ.