Trying to determine the purpose of sex without consulting its Creator is like trying to figure out how to operate a bulldozer without consulting the manual: You're not going to use it correctly, and somebody's probably going to get hurt. As we consult the scriptures, the purpose of sex is revealed and can be summarized by three words: Procreation, Pleasure, and Picture. It is the first of these that will be covered in this post.
Sex is everywhere. Billboards, TV, radio, the Internet, books, magazines, even casual conversation. You only need to stand in line at the grocery store for 45 seconds to see our culture's obsession with it. The mantra, "If it feels good, do it" is plastered on every conceivable surface where advertising space can be sold. Contrary to popular culture, however, the primary purpose for sex is procreation - the creation of children. There is no denying that God designed it to be pleasurable, but let us look at the first command God issues to Adam and his wife. In Genesis 1:27-28, He commands them to "be fruitful and multiply and fill the earth." It is the design and plan of the Creator for His people, within the protection of marriage, to have children. It is God's first command to His people.
Obedience to this command means we will have children. As with the purpose of sex, we must push against the culture here and look to the Creator for clarity on this subject. Our culture typically views children as a burden, something that must be tolerated and dealt with in a "P.C.' manner until they can be a contributing member of the family or, indeed, society. We must, as in all things, heed the words of Paul: "Do not be conformed to this world, but be transformed by the renewal of your mind, that by testing you may discern what is the will of God, what is good and acceptable and perfect." (Romans 12:2)
As we turn to scripture we find a different view about children. Psalm 127:3-5 says this: "Behold, children are a heritage from the Lord, the fruit of the womb a reward. Like arrows in the hand of a warrior are the children of one's youth. Blessed is the man who fills his quiver with them! He shall not be put to shame when he speaks with his enemies in the gate." Clearly God has designated children as a blessing, not a burden. They are to be our primary focus of discipleship (Deuteronomy 6:4-9), and they will be a conduit of sanctification for us.
For clarification, procreation is not the sole purpose of sex. Women who are unable to conceive are still able to enjoy the pleasures of sex with their husbands, as are men who are infertile able to enjoy it with their wives. This is right and good. Often the blessing of adoption is found to be the vehicle by which these families, by God's grace, can redeem children who have been born outside of God's first command. While God's primary purpose for sex is procreation, the pleasure and the picture He chooses to bless the covenant of marriage with are not lost without the ability to procreate.
I am in a unique position to bear witness to the joys of procreation. As the director of Preschool Ministries for The Village Church, I am able to see the faces of the beautiful children that the Lord blesses the families of our church with. Every weekend, I see hundreds of children, from small infants to kindergarteners whom God has fortified with more energy than they know what to do with. It is my hope that these children are constant reminders of both God's love for us, and the truth that we will find joy in our obedience to Him - even in the first of His commands.