Short answer: Yes, incest is a sin in the Bible. The law given through Moses forbids sexual relations with a close relative, the New Testament still condemns it as sexual immorality, and the stories in Genesis never celebrate it. The earlier examples, such as Abraham marrying his half-sister, came before that law and do not make the practice right today.
In This Article
The subject is uncomfortable, and I will treat it plainly and without anything graphic. People ask the question for different reasons. Some are troubled by a critic who says the Bible contradicts itself. Some are asking about a painful situation in their own family. Some simply want to know where the lines are.
The critics say the Bible bans incest but then lets Abraham, Isaac and Jacob marry relatives. That is worth answering carefully, because the details matter.
What Are The Forbidden Relationships In The Bible?
The most thorough passage is Leviticus 18:6-18. It opens with a general rule and then names specific relatives.
No one is to approach any close relative to have sexual relations. I am the LORD.
Leviticus 18:6 (NIV)
The passage goes on to forbid relations with a mother, a father's wife, a sister or half-sister, a granddaughter, an aunt, a daughter-in-law and a sister-in-law, among others. Even someone related only through marriage falls under God's no. Leviticus 20:11-17 repeats several of these prohibitions and attaches severe penalties, including death, in the case of certain unions. Those penalties belonged to the civil law of ancient Israel. They show us how seriously God regards the sin, even though Christians are not under that legal code today.
The wording "I am the LORD" is not decoration. It reminds us that the standard comes from God himself, not from a passing custom. Another passage in Deuteronomy (Deuteronomy 27:20-23) records curses on those who commit such acts.
Why Did Abraham, Isaac And Jacob Marry Relatives?
This is the heart of the critic's objection, so let us look at the cases one at a time.
Abraham married Sarah, who was his half-sister, and he says so himself (Genesis 20:12).
Besides, she really is my sister, the daughter of my father though not of my mother; and she became my wife.
Genesis 20:12 (NIV)
Isaac married Rebekah, who came from Abraham's extended family back in his old homeland (Genesis 24:1-4). Jacob later married Leah and Rachel, who were his cousins. These are relationships between relatives, and some are closer than others, but not all of them fall inside the lines Leviticus later draws. A marriage between cousins, for instance, is not on the Leviticus 18 list.
The key point is timing. Abraham lived centuries before the law came through Moses. The restrictions of the Law of Moses were binding on the people to whom it was given, and on those who lived under it until it was fulfilled in Christ (Colossians 2:13-17). God had not yet issued the specific command, and the Bible simply reports what these men did without holding it up as a model for us.
I should add the early human family to this. Adam and Eve's children could only marry within the family, because humanity began with one couple. That came long before any law and is a different situation from anything that followed.
What Does The Bible Show About Incest In Practice?
When the Bible describes actual acts of incest, it describes them as shameful and destructive. Lot's two daughters got their father drunk and had children by him (Genesis 19:30-38). Moses recorded it, but nothing in the account approves it. The story is told in a bleak light and the descendants, Moab and Ammon, become long-term enemies of Israel.
Other accounts are darker still. Reuben slept with his father's concubine, and Jacob heard about it (Genesis 35:22). Amnon assaulted his half-sister Tamar, and the fallout tore David's household apart (2 Samuel 13:1-22). Note that the Bible reports these things the way it reports every human failure: honestly, and without applause.
Incest very often overlaps with abuse, especially when an adult or an older relative exploits a child. If that is part of your story, please know that the sin belongs to the abuser and not to you. Our articles on rape and pedophilia speak to that, and a trusted counselor or the authorities can help you get safe.
What Does The New Testament Say About Incest?
Paul deals with a case in the church at Corinth, and he is shocked by it.
It is actually reported that there is sexual immorality among you, and of a kind that even pagans do not tolerate: A man is sleeping with his father's wife.
1 Corinthians 5:1 (NIV)
Paul's instruction is that the church should not carry on as though nothing were wrong. The man was to be put out of the fellowship (1 Corinthians 5:1-5), with the hope that he would be brought back to God. So the New Testament carries the same moral judgment, even though Christians are no longer under the Law of Moses as a legal code.
Incest is a form of sexual immorality, and it can also be a violation of trust that leaves lasting harm. God designed sex for the marriage of one man and one woman, and the family is meant to be a place of safety. Jesus raised the bar by saying that even looking at someone with lust is a sin (Matthew 5:28). See also whether sex is a sin in the Bible.
Can Incest Be Forgiven?
People sometimes ask whether this is a sin God will not forgive, or whether it is among the worst. The Bible does not make a short list of sins outside the reach of Christ's blood. The only sin called unforgivable is a settled, deliberate rejection of the Spirit's witness to Christ, and I discuss it in What Is The Unforgivable Sin?. Anyone who turns from sin and trusts Jesus can be forgiven, and our article on whether God forgives all sins says more.
Forgiveness does not erase consequences. It also does not excuse anyone from stopping an ongoing harm, reporting abuse, or protecting a child. Repentance means a real change, not only sorrow. For the wider picture, see our guide to what sin is.
Key Bible Verses About Incest
- Leviticus 18:6: the general ban on relations with close relatives.
- Leviticus 18:6-18: the detailed list of forbidden relationships.
- Leviticus 20:11-17: the penalties under the law of Israel.
- Deuteronomy 27:20-23: curses on those who commit these sins.
- 1 Corinthians 5:1-5: Paul's judgment of a case in the church.
- Genesis 19:30-38: Lot and his daughters, told without approval.
- Matthew 5:28: Jesus on lust in the heart.
The Bottom Line
The Bible forbids incest, condemns it in the Law and in the New Testament, and never presents it as pleasing to God. The older family marriages in Genesis came before the commands in Leviticus and are not given as examples to follow. Hold the standard with seriousness, and hold out the gospel of forgiveness with equal seriousness.
Frequently Asked Questions
What are the forbidden relationships in the Bible?
Leviticus 18:6-18 lists close relatives with whom sexual relations are forbidden, including a mother, sister, granddaughter, aunt and daughter-in-law. Leviticus 20 repeats many of these with severe penalties under the law given to Israel.
Is it a sin to marry your brother or sister?
Yes. Under the Law of Moses, marrying a sister or half-sister is forbidden, and the New Testament still treats incest as sexual immorality. Abraham's marriage to his half-sister Sarah came before that law was given.
Did Adam and Eve's children commit incest?
The first human family descended from one couple, so their children had to marry within the family. That was before God's later commands, and the Bible does not treat it as the same thing as the sins condemned afterward.
Can God forgive incest?
Yes. Repentance and faith in Christ cover every sin, including this one, though forgiveness does not remove earthly consequences or the duty to protect victims. See Does God Forgive All Sins?
What sins will keep you out of heaven?
Scripture lists many sins that characterize a life apart from God, and it also says Christ's blood cleanses those who repent and believe. For the larger question see What Is The Unforgivable Sin?
