Abraham married his sister:

11 Abraham said, “I did it because I thought, ‘There is no fear of God at all in this place, and they will kill me because of my wife.’ 12 Besides, she is indeed my sister, the daughter of my father though not the daughter of my mother, and she became my wife. [Genesis 20:11-12 ESV]

And God blessed this marriage:

15 And God said to Abraham, “As for Sarai your wife, you shall not call her name Sarai, but Sarah shall be her name. 16 I will bless her, and moreover, I will give you a son by her. I will bless her, and she shall become nations; kings of peoples shall come from her.” [Genesis 17:15-16 ESV]

However, incestuous relationships are explicitly prohibited in Scripture:

22 “‘Cursed be anyone who lies with his sister, whether the daughter of his father or the daughter of his mother.’ And all the people shall say, ‘Amen.’ [Deuteronomy 27:22 ESV]

17 “If a man takes his sister, a daughter of his father or a daughter of his mother, and sees her nakedness, and she sees his nakedness, it is a disgrace, and they shall be cut off in the sight of the children of their people. He has uncovered his sister's nakedness, and he shall bear his iniquity. [Leviticus 20:17 ESV]

How can we reconcile all this?

  • You've given no reason to suppose that laws from hundreds of years after Abraham applied to him.
    – curiousdannii
    Commented Mar 22, 2021 at 5:24
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    @curiousdannii - are you suggesting that God's laws are not eternal?
    – user38524
    Commented Mar 22, 2021 at 5:26
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    People mean different things by that. I'm just saying that you obviously have some presuppositions that would help your question be understood, and you should explain them. If someone read your question with no theological background they'd have every right to think that it makes as much sense as asking how Abraham having slaves and servants wasn't a violation of the US 13th amendment. And in general, you shouldn't assume a flat timeless reading of scripture on this site. While some Christians do read the Bible that way, most don't, especially not those in more academic circles.
    – curiousdannii
    Commented Mar 22, 2021 at 5:29
  • There is at least one law of God that is not eternal... the law forbidding marrying a sister. If this were not so then Cain, Abel and Seth had no one to marry. Commented Jun 11 at 14:49

6 Answers 6


There are two matters here:

  1. Marrying siblings was not always a problem but became a problem (as we now know) because of biological problems. Adam and Eve's children must have (almost) all married their siblings!!
  2. The prohibition against marrying siblings (Deut 27:22, Lev 20:17) only became an Israelite law under the the Levitical system that was given about 2500 years after creation and more than 400 years after Abraham. It did not exist before.

Thus, there was nothing prohibiting Adam and Eve's children and Abraham marrying their siblings. As time progressed, this restriction was introduced to prevent birth problems (as we now understand).

  • 1
    You mentioned “biological problems” in sibling marriages. Do you have a reference for that? A link would be good. The reason I am asking is mainly not because of genetically incompatibility, but rather of infertility. The Bible makes it ckear that Sarah was infertile for most of her life, not giving birth until she turned 90. What is interesting, but not too obvious, is that the timespan between births in early Genesis also was quite long. Commented Mar 21, 2021 at 22:58
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    @Constantthin - I think this is common knowledge. However, for a general reference see en.wikipedia.org/wiki/Incest and the problem of inbreeding and genetic defects.
    – Dottard
    Commented Mar 21, 2021 at 23:00
  • You wrote: “Adam and Eve's children must have (almost) all married their siblings!!” That doesn’t have to be true. Adam and Eve would have had many children during their 900 odd years on earth. Only the first one to two generations could have married their siblings. Mathematically it would have been enough for only Cain to have married his sisters during the first hundred years. Set could have been 105 years old when first becoming a dad, and could then have married on of Cains daughters. Commented Mar 24, 2021 at 22:34
  • @Constantthin - that is theoretically correct. By statement was deliberately vague because we do not know how many children Eve produced and over what time. Did she become menopausal at 100, 200 or 500 years? We are not told. Nor do we know how long she lived.
    – Dottard
    Commented Mar 24, 2021 at 22:39

Technically, Sarah was Abraham’s HALF-sister, according to Genesis 20:12:

Besides, she is indeed my sister, the daughter of my father though not the daughter of my mother, and she became my wife.

There are two occasions when Abraham was less than honest regarding his relationship with Sarah, his wife. The first instance is mentioned in Genesis 12:10-20 when famine drove Abraham down to Egypt. Abram feared that the Egyptians would kill him because Sarai was beautiful and they would want her as a wife. So he asked Sarai to tell everyone that she was his sister—which was technically true but also meant to deceive. Sarai was taken into Pharaoh’s house, and Abram was treated well because of her. But God afflicted Pharaoh’s house, and the lie was revealed. Pharaoh returned Sarai to Abram and sent them on their way.

The other is recorded in Genesis 20:1-18 when Abraham told Abimelech, king of Gerar, that Sarah was his sister. Sarah was also complicit, but God prevented Abimelech from having his way with Sarah. Abraham was caught out and that’s when he confessed he was afraid he might be killed and that they were actually half-brother-and-sister.

Back then genetics were purer than they are today, and because people lived together in close family units, it was common for a man to find a wife from within their own tribe and family.

However, as you point out from Deuteronomy 27:22 and Leviticus 20:17, incestuous relationships are explicitly prohibited. But those laws did not exist during Abraham’s life time. God’s laws were given to the Israelites about 1,000 years later. These laws were given by God to keep his people holy and clean, and to prevent them from being polluted by the pagan nations.

Why did God bless Abraham, even though he married his half-sister? God had plans for Abraham and for Sarah, namely that the Messiah would come through their son Isaac.

  • I don't mean this as criticism of Lesley or of the answer, but that very last sentence jarringly reminded me why this site failed so badly in its mandate. The failure was predictably inevitable, but unfortunate nonetheless. See cellio | Biblical Hermeneutics site: mostly harmful Commented Mar 21, 2021 at 15:25
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    @RayButterworth - No offence taken, but having read the information in that link about BH, I've removed the last sentence. Thanks for the heads up.
    – Lesley
    Commented Mar 21, 2021 at 15:34
  • The first sentence should probably be removed too, since both quoted scripture snippets in the question make quite clear half siblings still count. There is no "technicality" there.
    – T.E.D.
    Commented Mar 21, 2021 at 15:46
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    “You wrote that “back then genetics were purer than they are today”. Do you have a reference for that statement? Commented Mar 21, 2021 at 22:53
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    @Constantthin - again, that is common knowledge - the genome decays with each generation as new errors occur.
    – Dottard
    Commented Mar 21, 2021 at 23:03

When I call you a brother, it does not automatically mean blood brother, it can mean from the same religion, from the same nation, or even as in general we are all brothers and sisters.

In Islam, when Abraham called her his sister, he meant that as a sister in religion, and that was to protect her. This is not lying, it is a statement with multiple meanings. Our understanding of scriptures is built on certain foundations, and one of these is that prophets can not lie.

More info on the Islamic stance can be found on IslamicFinder.org website.

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    – agarza
    Commented Mar 23, 2021 at 16:52
  • 2
    This explanation of the use of "sister" seems plausible, but how does it account for Abraham's further statement that Sarah is "the daughter of my father though not the daughter of my mother"?
    – DLosc
    Commented Mar 10, 2022 at 16:56

Romans 5:13. “For sin indeed was in the world before the law was given, but sin is not counted where there is no law”. I’d encourage you to read Romans5:12-14.

  • 1
    This makes it sound like Abraham and Sarah were sinning by being in a incestuous relationship, and so God shouldn't have blessed their marriage. While I agree that sin exists without the law, as all rebellion against God is sin, what specifically is there that makes you think that incest was sin at the time of Abraham? Please edit this to explain in much more detail.
    – curiousdannii
    Commented Dec 5, 2022 at 13:00
  • What of Adam and Eve's children - all married their siblings. It was only at Sinai that sibling marriages were prohibited.
    – Dottard
    Commented Dec 15, 2022 at 21:28
  • @curiousdannii Why stop at incest then? Why not include murder and corruption also as not sins at the time? Are there specific scriptures detailing what was and was not considered sin at that time? If not, there isn't really much basis for this argument. The qualm is in allowing a certain act which would later be labelled as a great sin; it violates the eternal aspect of the scripture.
    – Samid
    Commented Sep 25, 2023 at 12:51

It is true that the law forbidding incestuous relationship was not in Vogue during the life time of the Patriarch Abraham. God's laws concerning the guidance of man in their earthly existence permit me to say, sometimes may not be static. These laws which violation brings about the concept of sin, are usually dynamic in response to times, situations and locations and should be understood as such. These are different from the immutable universal laws (including but not limited to the laws of sowing and reaping, gravity, minus and plus) representing the will of God in motion in the entire universal systems.

So, in the times of Father Abraham the term incest which is not only a sin but an abomination was not known and could not be considered sinful

Furthermore in response to time and location, the practice of mixed cropping amongst other things was considered sinful in the early years of the Israelites in the land of Canaan (see Deut 22:9-11). But in our present world such practices are encouraged and not considered sinful.

So, Father Abraham's marriage to Sarah his half-sister was not a sin and such union wouldn't hinder God's abundant blessings on him.

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    – agarza
    Commented Jan 7 at 13:44
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    – Community Bot
    Commented Jan 7 at 13:44

Potentially offensive not intended

The only logical conclusion other than being related by blood is to be related by marriage. This is to then say Sarai was Haran's wife, and therefore Abraham's sister-in-law. Upon Haran's death, she becomes Terah's daughter, and therefore Abraham's sister. Additionally, Lot and Milcah, upon becoming "fatherless", also become Terah's son and daughter, explaining further why Lot is referred to as Abraham's brother four times, and nephew only twice, in Genesis.

If this is the case, are Lot, Milcah, and Iscah Sarai's children, or children from a previous marriage? Although Genesis says "she had no child", this could be in relation to Abraham given that she was barren due to age. It would also explain why Lot stayed with Abraham and Sarai, and why Abraham did his best to look after him. Leviticus also forbids sexual relations between a man and his brother's wife, but not marriage.

Abraham could have married Sarai because it was the most righteous action at the time, knowing full well that he would not be having sexual relations with her. This shows a great amount of respect for both Abraham and Sarai, and I propose this is the main reason why God called him to become a Father of Nations. In fact, marrying Sarai is the only action he takes that we know of before he is called out.

The many mentions of God protecting the widow and the fatherless in many Psalms (including 146) would also make sense. Milcah becoming a sister to Sarai through Terah would explain why Sarai is considered to be Iscah.

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