Short answer: In the Bible, sexual immorality (the Greek word is porneia) means any sexual activity outside the marriage of one man and one woman. That includes adultery, sex before marriage, pornography, same-sex relations and the other sexual acts Scripture forbids. The Bible treats these as sin against God and against our own bodies, and it also promises full forgiveness to anyone who repents.
In This Article
Few words in the New Testament are as often misunderstood as this one. Some people read it as a ban on anything remotely romantic. Others say it only means adultery, and that everything else is a matter of personal choice. People ask me where the lines are, because they want to do what God asks and the old translations are vague.
I will go through this carefully. The article covers what the word means, where the Bible draws its boundaries and why, the questions people most often raise about kissing, marriage and the body, and the good news of forgiveness for those who have fallen short.
What Is Sexual Immorality In The Bible?
The New Testament word is porneia. Older translations render it fornication, and our word pornography comes from the same root. It is a wide word. It covers sexual sin in general and not just one act, and a New Testament writer who wants to warn about sexual sin uses it as the umbrella term. Jesus used it in his teaching, and Paul used it in nearly every letter. I explore the word in Defining Porneia In The Bible.
Sexual immorality therefore means sexual activity that falls outside what God designed. That design is stated in the opening chapters of Scripture.
That is why a man leaves his father and mother and is united to his wife, and they become one flesh.
Genesis 2:24 (NIV)
Jesus quoted this verse when he was asked about marriage (Matthew 19:4-6). It tells us that God made sex for a covenant between one man and one woman, a lifelong commitment, and that the union is meant to be exclusive. So porneia names whatever departs from that: sex before marriage, sex with someone else's spouse, sex that is bought or sold, and sexual conduct God's word rules out.
What Does The Bible Say About Sexual Immorality?
The Bible speaks about this plainly and often. Marriage, it says, is to be honored, and the marriage bed kept pure.
Marriage should be honored by all, and the marriage bed kept pure, for God will judge the adulterer and all the sexually immoral.
Hebrews 13:4 (NIV)
The main categories are these.
Adultery. The seventh commandment forbids it (Exodus 20:14), and Jesus extended it to the heart (Matthew 5:27-28). See Is Adultery A Sin In The Bible?
Sex before marriage. Fornication is sexual activity between people not married to each other. Scripture treats it as sin and urges believers to flee it (1 Corinthians 6:18). See Is Premarital Sex A Sin? and living together outside marriage.
Pornography and lust. Jesus said that looking at a woman with lust is already adultery of the heart. That is why I include pornography and lust here, even though no physical act takes place.
Same-sex relations. Romans 1:26-27 and Leviticus 18:22 describe same-sex intimacy as outside God's design, and I hold that the Bible's teaching here is consistent with its teaching on all sexual sin. I have written about it with care in What Does The Bible Say About Homosexuality? The Bible also says that attraction is not the same as acting on it, and that every person is made in God's image.
Other forbidden unions. Leviticus 18 lists incest, bestiality and other practices God forbids (Leviticus 18). See Is Incest A Sin? and Examples Of Sexual Sin In The Bible.
Why Is Sexual Sin Called A Sin Against The Body?
Paul's wording in 1 Corinthians 6 surprises many readers.
Flee from sexual immorality. All other sins a person commits are outside the body, but whoever sins sexually, sins against their own body.
1 Corinthians 6:18 (NIV)
Paul is not saying other sins do no damage. He is saying that sex involves the body in a way that touches the whole person. The verses around it say that the body of a believer is a member of Christ and a temple of the Holy Spirit, and that sexual union is not a casual act but one that joins two people together. To use the body for what God has not designed is to damage something that belongs to him.
The Bible also notes real consequences. Sexual sin breaks marriages, wounds families, spreads disease, brings guilt and shame, and can lead to unplanned pregnancy. Paul warns that the sexually immoral will not inherit the kingdom of God (1 Corinthians 6:9-10). But read the verse after it, because it matters.
Is Kissing Or A Sexless Marriage Sexual Immorality?
These two questions come up often, and both need more care than a quick yes or no.
Kissing. The Bible does not label a kiss as porneia, and it describes romantic affection without embarrassment. The question is what it is leading to. Kissing can be a warm and fitting part of a courtship, and it can also be the first step on a road toward what Scripture warns against. Each couple has to be honest about where it leads them. I take this up in Is Kissing Or Making Out A Sin?
Marital intimacy. The Bible is not shy about the goodness of sex in marriage. Proverbs 5:19 tells a husband to let his wife's breasts satisfy him always, and to be captivated by her love. That is the context for the line often quoted. It is the Bible telling a husband that the answer to temptation is delight in his own spouse, not suppression. Paul goes on to tell married couples that they owe one another physical love and should not withhold it except for a short time by agreement (1 Corinthians 7:3-5). Illness, trauma, age and grief can make intimacy hard, and none of those is sin. A lasting, willful refusal of one's spouse, though, is a serious thing to bring to a pastor or counselor. If you are in that situation, please do not stay silent.
What Is The Worst Sin, And Does God Forgive Sexual Sin?
People often ask whether sexual sin is the worst kind. Scripture does not rank sins that way, though it does say sexual sin is unusual in how it touches the body. The question of a single worst sin is covered in The Greatest Sin In The Bible, and the question of whether all sins weigh the same in Are All Sins Equal?
What matters more is what comes next. Sexual sin is not unforgivable. Paul gave his list of the sinners who will not inherit the kingdom, and then said something to the church members who had lived that way.
And that is what some of you were. But you were washed, you were sanctified, you were justified in the name of the Lord Jesus Christ and by the Spirit of our God.
1 Corinthians 6:11 (NIV)
The one sin the Bible says will not be forgiven is not sexual. See What Is The Unforgivable Sin? For everything else, the promise stands: if we confess, he is faithful and just to forgive us and cleanse us (1 John 1:9).
How Do I Start Over?
Begin with honesty before God, with no excuses. Turn away from the practice, cut off whatever feeds it, and ask for help from a mature believer. Shame will tell you to hide, and that is the opposite of what heals. See How To Repent, Confess Your Sins To One Another and How Can We Overcome Sins? A person who has fallen is not finished. Grace is stronger than the failure.
Key Bible Verses About Sexual Immorality
- Genesis 2:24: God's design is one man and one woman, becoming one flesh.
- Hebrews 13:4: keep the marriage bed pure; God judges the sexually immoral.
- 1 Corinthians 6:18: flee sexual immorality, a sin against the body.
- 1 Thessalonians 4:3-5: God's will is that we avoid sexual immorality and control our bodies.
- Proverbs 5:18-19: a husband is to delight in his own wife.
- 1 Corinthians 6:11: you were washed, sanctified and justified.
- 1 John 1:9: God forgives and cleanses those who confess.
Frequently Asked Questions
Why does the Bible say "Let her breast satisfy you"?
Proverbs 5:19 is addressed to a husband, urging him to find delight in his own wife. The Bible does not treat marital intimacy as shameful. It celebrates it, and the Song of Songs does so at length. The verse is not a license for lust. It is the positive side of the boundary: sexual desire is good and belongs inside marriage.
Why is fornication a sin against the body?
Paul says in 1 Corinthians 6:18 that sexual sin is sin against one's own body. In context, he explains that the body of a believer belongs to the Lord and is a temple of the Holy Spirit, and that sexual union joins two people in a way that is not meant to be casual. The harm is to the whole person, not only to behavior.
Is kissing sexual immorality?
The Bible does not call kissing sexual immorality, and it records affectionate kissing in the Song of Songs. The concern is where desire is heading and whether it is being stirred up for someone you are not married to. See Is Kissing Or Making Out A Sin?
Is a sexless marriage a sin?
Scripture does not say that a marriage without sex is automatically sinful, since illness, grief, age and pain are real. But Paul teaches that spouses owe each other their bodies and should not deprive one another except by agreement for a short time (1 Corinthians 7:3-5). A deliberate, lasting refusal is a problem to bring to a pastor or counselor.
What sins does God not forgive?
The Bible names only one sin that will not be forgiven, and it is a persistent rejection of the Holy Spirit's testimony to Christ, not a sexual sin. Sexual sin is forgiven when a person repents and trusts Christ. See What Is The Unforgivable Sin? and Does God Forgive All Sins?
