In the proper setting, sex is not a sin. In fact, sex is God’s idea. In Matthew 19:4–6, Jesus states with godly authority, “At the beginning the Creator ‘made them male and female,’ and said, ‘For this reason a man will leave his father and mother and be united to his wife, and the two will become one flesh.’ So they are no longer two, but one flesh. Therefore what God has joined together, let no one separate.” The creation account is thus the foundation for the institution of marriage, which was validated by the Creator Himself and established to be a lifelong union between one man and woman.
The very fact that God created humanity as “male and female” reveals that we are created as sexual beings. And God’s command to “be fruitful and multiply” cannot be fulfilled without sex (Genesis 1:28). Sex is a God-given mandate, so there is no way that sex is a sin if done with one’s lifelong marriage partner of the opposite sex.
The word sex is not found in the Bible. The numerous mentions of the word in society, and the world’s tendency to sneer, have given the word a certain amount of notoriety. But God never intended it to be a dirty word.
The Song of Solomon follows a loving relationship between a husband and his wife through the betrothal period, wedding night, and beyond. The description of the husband and wife’s pleasure in chapter 4 is discreet yet unmistakable in its meaning. That description is followed in 5:3 with God’s approval: “Eat, friends, and drink; drink your fill of love.”
It is only outside of marriage that sex is sinful. God made it very certain that the marriage bed must be kept pure (Hebrews 13:4). Sexual activity outside of marriage is called fornication. First Corinthians 6:9–10 says, “Do you not know that wrongdoers will not inherit the kingdom of God? Do not be deceived: Neither the sexually immoral nor idolaters nor adulterers nor men who have sex with men … will inherit the kingdom of God” Engaging in sex without the benefit of marriage is immoral, and “it is God’s will that you should be sanctified: that you should avoid sexual immorality” (1 Thessalonians 4:3; cf. 1 Corinthians 6:18).
If the Bible’s message on abstaining from sex until married were upheld, there would be far fewer sexually transmitted diseases, far fewer abortions, far fewer unwanted pregnancies and unwed mothers, and far few children growing up without both parents in their lives. Abstinence saves lives, protects babies, gives sexual relations the proper value and, most importantly, honors God.
In no way is sex between a husband and wife a sin. Rather, it is a beautiful expression of love, trust, sharing, and unity. Sex is God’s gift to a married couple for pleasure and procreation.
 Got Questions Ministries. (2010). Got Questions? Bible Questions Answered. Bellingham, WA: Logos Bible Software.