"Flee fornication. Every sin that a man doeth is without the body; but he that committeth fornication sinneth against his own body."
Bible Definition of Fornication
From the King James Dictionary, Fornication is defined as "Sexual immorality. Be ye therefore followers of God, as dear children; and walk in love, as Christ also hath loved us, and hath given himself for us an offering and a sacrifice to God for a sweetsmelling savor. But FORNICATION, and all uncleanness, or covetousness, let it not be once named among you, as becometh saints; neither filthiness, nor foolish talking, nor jesting, which are not convenient: but rather giving of thanks." (Ephesian 5:1-4)
What Is Fornication?
The following text is from Russell Moore's blog post "Premarital Sex?":
Christians talk a lot about premarital sex. And I think that’s a mistake. I don’t think it’s a mistake because the issue is unimportant but because the grammar is skewed. The word “fornication” is almost gone from contemporary Christian speech. It sounds creepy and antiquated. Instead, we talk about “abstinence” and “premarital sex.”
According to Russell Moore, the loss of the words “fornicate” and “fornication” implicitly cedes the moral imagination to the sexual revolutionaries because the words “fornication” and “premarital sex” aren’t interchangeable. Fornication isn’t merely “premarital.” Premarital is the language of timing, and with it, we infer that this is simply the marital act misfired at the wrong time. But fornication is, both spiritually and typologically, a different sort of action from the marital act. That’s why the consequences are so dire.
Fornication pictures a different reality than the mystery of Christ presented in the one-flesh union of covenantal marriage. It represents a Christ who uses his church without joining her, as a covenant and permanently, to himself. The man who leads a woman into the sexual union without a covenantal bond is preaching to her, to the world, and to himself a different gospel from the gospel of Jesus Christ. And he is forming a real spiritual union, the Apostle Paul warns, but one with a different spirit than the Spirit of Christ (1 Corinthians 6:15).
The Dangers of Fornication
This is important because the Scripture makes clear that “fornicators will not inherit the kingdom of God” (1 Cor. 6:9-10; Revelation 21:8). The language of “premarital sex” can enable conscience to evade repentance. After all, if the problem is one merely of “timing” or of “waiting” then the problem is resolved once one is married. The event was in the past.
This makes fornication even more dangerous, in this sense than adultery. Both fornication and adultery are acts of infidelity. But a man who has committed adultery, if he is repentant, understands something of how he’s broken trust, attacked a covenant. He can see that even when his wife has forgiven him, he must invest years in rebuilding trust. He can understand why his wife concludes that if he’ll cheat with one woman, why would he not cheat with another? He must work to show himself faithful.
The fornicator can be deceived into thinking that marriage has solved the problem. He doesn’t see the ongoing nature of the problem. Often he finds it difficult to lead his wife spiritually or to fully gain her trust. The root problem is a sin committed together, driving the couple apart.
Fornication and Adultery
Moreover, she knows, especially if he professed to be a Christian before the marriage, that his libido is stronger than his conscience. If he’s able to justify his fornication, he will justify his adultery. They are not two separate things, but two different phases of the same thing: immorality in contrast to the self-giving and uniting covenant of marriage.
We ought not to be ashamed of the Christian language of “fornication,” but instead to be ashamed of fornication itself.
That doesn’t make us more censorious. When we speak honestly, we are able to speak with more liberating power to sinners, including sexual sinners, in our streets and sidewalks, and pews. The blood of the cross can cleanse any sin, but no one comes to the cross without repentance. When we speak bluntly and honestly we lead people to the cross—to repent, not just to rebrand.
(Excerpt from Russell Moore's: Premarital Sex?)
Bible Verses about Fornication and Sexual Immorality
Let marriage be held in honor among all, and let the marriage bed be undefiled, for God will judge the sexually immoral and adulterous. ~ Hebrews 13:4
Flee from sexual immorality. Every other sin a person commits is outside the body, but the sexually immoral person sins against his own body. Or do you not know that your body is a temple of the Holy Spirit within you, whom you have from God? You are not your own, for you were bought with a price. So glorify God in your body. ~ 1 Corinthians 6:18-20
But because of the temptation to sexual immorality, each man should have his own wife and each woman her own husband. ~ 1 Corinthians 7:2
Now the works of the flesh are evident: sexual immorality, impurity, sensuality, idolatry, sorcery, enmity, strife, jealousy, fits of anger, rivalries, dissensions, divisions, envy, drunkenness, orgies, and things like these. I warn you, as I warned you before, that those who do such things will not inherit the kingdom of God. ~ Galatians 5:19-21
And he said, “What comes out of a person is what defiles him. For from within, out of the heart of man, come evil thoughts, sexual immorality, theft, murder, adultery, coveting, wickedness, deceit, sensuality, envy, slander, pride, foolishness. All these evil things come from within, and they defile a person. ~ Mark 7:20-23
You are doing the works your father did.” They said to him, “We were not born of sexual immorality. We have one Father—even God.” Jesus said to them, “If God were your Father, you would love me, for I came from God and I am here. I came not of my own accord, but he sent me. ~ John 8:41-42
Put to death therefore what is earthly in you: sexual immorality, impurity, passion, evil desire, and covetousness, which is idolatry. ~ Colossians 3:5