When we think of sexual purity, our culture brings to mind a maiden, sitting in the forest, with a unicorn’s head in her lap. Others think of a bride presenting herself for the first time to her groom on their wedding night. But keeping sex for marriage is both more and less sacred. Virginity is not something to be worshiped. It’s not about cultural shame. It’s about the way God designed us and the really hard battle of following Him.
There are three serious reasons to save sex for marriage. First, because as believers, we are to obey what God tells us to do. 1 Corinthians 6:18–20 states, “Flee from sexual immorality. All other sins a person commits are outside the body, but whoever sins sexually, sins against their own body. Do you not know that your bodies are temples of the Holy Spirit, who is in you, whom you have received from God? You are not your own; you were bought at a price. Therefore honor God with your bodies.” If we are in Christ, we have allowed Him to purchase us with the sacrifice of His blood. In exchange for eternal life, we are to trust that He knows what is best for us, and obey Him.
The second reason is similar. Like any sin, avoiding sexual immorality is a contest of our new nature in Christ and our fleshly desires. 1 Thessalonians 4:3–7 says, “It is God’s will that you should be sanctified: that you should avoid sexual immorality; that each of you should learn to control your own body in a way that is holy and honorable, not in passionate lust like the pagans, who do not know God; and that in this matter no one should wrong or take advantage of a brother or sister. The Lord will punish all those who commit such sins, as we told you and warned you before. For God did not call us to be impure, but to live a holy life.” Allowing your body to control your actions is an act of defiance against God. Godly sex is giving. Using someone else to fulfill a desire of the flesh is selfish and abusive. Even if the partner is willing, you are still helping them to sin and negatively altering their relationship with God and others.
The final reason is somewhat more practical. Paul talked of the “mystery” of marriage (Ephesians 5:31). When God spoke of two people being joined as one, He was referring to something we’re only beginning to understand in a real, physiological way. When two people are intimate, the hypothalamus releases chemicals that induce feelings of attachment and trust. Having sex outside of marriage means allowing your body to attach to and trust someone who you do not have a committed relationship with. The definition of trust in the mind deteriorates. To have that kind of link with someone without the security of being in the state of working together toward God is dangerous. Two individuals who are—even mildly—physiologically obsessed with each other but not committed to growing in God as a couple can be torn apart from God and His plans for them.
Conversely, if two people make a conscious, deliberate choice to commit, and then allow the intimacy that releases these chemicals, the body can reaffirm the connection the mind has made. The physiological feelings of trust and attachment are reinforced by the reality of the relationship. In this way, two people become one in a physical way that reflects what God has done spiritually.
The purpose of marriage is to reflect the relationship between the church and Christ and to serve God as a strong, unified partnership. Sex, along with procreation, was designed by God to strengthen that partnership. Sex outside of marriage creates bonds that tear apart people’s hearts instead of joining them together. God can redeem anyone, and He can heal someone who has indulged their flesh instead of controlling their desires. But God designed couples to be joined—spiritually, physically, and physiologically—from a state of purity.
 Got Questions Ministries. (2010). Got Questions? Bible Questions Answered. Bellingham, WA: Logos Bible Software.