What does the Bible say about sex before marriage?
Scripture addresses sexual intimacy outside of marriage with a single, unambiguous word: fornication (Greek porneia). It is forbidden — not as an arbitrary rule, but because of the profound dignity God has given the human body.
The Body Belongs to the Lord
The fullest treatment comes in 1 Corinthians 6, where Paul makes a striking argument. The body is not a temporary vessel to be used at will — it is "for the Lord, and the Lord for the body." Because the believer's body is a member of Christ and a temple of the Holy Spirit, sexual union outside marriage is a sin against one's own body in a way no other sin is.
William Kelly expounds on this passage at length:
William Kelly"The body [is] not for fornication but for the Lord, and the Lord for the body. And God both raised the Lord, and will raise up us by his power. Know ye not, that your bodies are members of Christ? Shall I then taking the members of Christ make [them] members of a harlot? Let it not be. ... Flee fornication. Every sin which a man may practise is outside the body, but the fornicator sins against his own body. What! Know ye not that your body is a temple of the Holy Spirit that [is] in you, which ye have from God; and ye are not your own? For ye were bought with a price: do then glorify God in your body."
Kelly draws out the two great motives for personal purity:
"Its incongruity with our relation to Christ is not all that the apostle urges. Fornication he would have avoided earnestly, because of its peculiar character, differing as it does from every other sin in this that it is against the body itself, while others are external to it. How dreadful then to think not merely of the body so misused, but the Christian's body, temple of the Holy Spirit as it is! not from any mere consecration to Him but from His being in us, and this from God, on the ground of purchase by Christ's blood."
J. N. Darby puts it concisely:
J. N. Darby"All fornication is forbidden. To us, with our present Christian habits of mind, it is a thing of course — to Pagans, new; but the doctrine exalts every subject. Our bodies are the members of Christ. ... Our bodies are His temples. What a mighty truth when we think of it! Moreover we are not our own, but were bought with a price — the blood of Christ offered for us. Therefore we ought to glorify God in our bodies, which are His."
Sanctification: God's Will for Believers
In 1 Thessalonians 4:3-8, Paul is equally direct: "This is the will of God, your sanctification, that ye abstain from fornication." The exhortation was especially needed in a Greco-Roman world where sexual impurity was not even counted as sin.
William Kelly explains the weight of this:
William Kelly"On one thing especially was the apostle urgent, the personal purity of those who bore the name of Jesus; and the more so as the Greeks utterly failed in it. Their habits and their literature, their statesmen and their philosophers, all helped on the evil; their very religion conduced to aggravate the defilement by consecrating that to which depraved nature is itself prone. ... Christ changed all for those who believe in Him, leaving an example that they should follow His steps."
J. N. Darby observes that the body was treated as a mere instrument in pagan culture, but Christianity placed it on entirely new ground:
J. N. Darby"The body was but as a vessel to be used at will for whatever service they chose. They were to possess this vessel, instead of allowing themselves to be carried away by the desires of the flesh; because they knew God."
Hamilton Smith highlights the contrast:
Hamilton Smith"God's will is that we walk in practical sanctification that abstains from lust, and holds these human vessels as set apart for honourable uses, and not merely for the gratification of evil passions as with those who know not God."
Marriage Is God's Provision
The reason Scripture forbids fornication is not that sexuality is evil, but that it is sacred — designed for the marriage relationship. Kelly notes Paul's instruction in 1 Corinthians 7:
"On account of fornications, let each have his own wife, and each have her own husband."
And he adds:
"It was he who still later wrote to the Hebrews, Let marriage be every way honourable, and the bed undefiled."
Darby, commenting on Hebrews 13, lists the positive duty alongside the negative:
"Brotherly love, hospitality, care for those in bonds, the strict maintenance of the marriage tie and personal purity, the avoiding of covetousness: such are the subjects of exhortation."
The Danger of a Little Evil
Writing on Ephesians 5, where Paul warns that "fornication and all uncleanness, or covetousness, let it not be once named among you, as becometh saints," W. Kelly presses the seriousness of even small compromises:
"There is another thought along with it which seems to me of value — that sin, when looked at in the presence of God, always acquires its true name and character. I am not allowed to gloss over it, and call it by a name that men might give it."
"What an effect of a moment's gratification! If then a little word is as the letting out of water, what is a little act of sin, where it is allowed? The Lord keep us from little sins — keep us watchful, jealous, careful; but at the same time never letting slip grace."
A Clear Answer
The biblical testimony is consistent and emphatic. Sexual intimacy is designed by God for the marriage bond, and fornication — any sexual union outside that bond — is explicitly and repeatedly forbidden. But the motive Scripture gives is not mere prohibition: it is the staggering truth that the believer's body is a temple of the Holy Spirit, purchased at the price of Christ's blood. As Darby summarises: "Our true liberty is to belong to God. All that is for oneself is stolen from the rights of Him who has bought us for His own."