Was the marriage between Abraham and Sarah incestuous?

"If Sarai (later Sarah) was the daughter of Terah, then Sarai would have been listed along with Abram, Nahor, and Haran.

So we can confirm that the intended meaning was cousin."

Hmm, but in Genesis 20 Abraham says ...

Abraham replied, “I said to myself, ‘There is surely no fear of God in this place, and they will kill me because of my wife.’ 12 Besides, she really is my sister, the daughter of my father though not of my mother; and she became my wife.

... So I guess she was his half-sister and the marraige very much was an incestuous one.

Abraham married his wife before his calling from God and before the 10 commandments. Every wrong action after the 10 commandments is a sin.

Sibling marriage, and later, "near kin" marriage, was the only initial option; the limited selection repeated with Noah's 3 sons and their wives following the great flood. Just 340 year later Abram, was 10 when his half-sister Sarai was born. During this time period sibling and "near kin" marriage was less common, but not certainly accepted and not prohibited yet; even forms of endogamy was still practiced at this time. Genesis 19:30-38 shows a good example of the times when the daughters of Abram's nephew, Lot, sleep with their father Lot out of necessity of circumstance; endogamy is demonstrated when Jacob, then Abraham's grandson, was instructed by his father Isaac to seek a marriage within the family, and Rebekah, daughter of Bethuel the son of Milcah, the wife of Abraham’s brother Nahor was chosen by God to be Isaac's wife. It was over 500 years later that near kin marriage was declared as wrong within Leviticus 18, 20 and Deuteronomy; it's interesting to note that marriage between a man and his step sister, his wife's niece or daughter are not prohibited specifically anywhere in those texts.

In Genesis 11:31 the KJV reads "And Terah took Abram his son, and Lot the son of Haran his son's son, and Sarai his daughter in law, his son Abram's wife; and they went forth with them from Ur of the Chaldees, to go into the land of Canaan; and they came unto Haran, and dwelt there."

Why would it say "Sarai his daughter in law" if she was in fact Terah's daughter? It would be shorter and more accurate to say "Sarai his daughter, his son Abram's wife" rather than "Sarai his daughter in law, his son Abram's wife" as it does. Was the fact that she was married to Abraham more relevant in a patriarchal society, so that it should be repeated twice while leaving out the father-daughter relationship? Or perhaps the author of Genesis 11 wanted to obscure the fact that Abraham had committed incest? None of these seem very satisfactory to me.

This induces me to consider that in Genesis 20:12, Abraham is lying again to Abimelech, in order to cover up the fact that he lied about Sarah being his sister. He said she was his sister in order to deceive Abimelech about her being his wife, and now he's saying that she's his half-sister in order to deceive Abimelech about the fact that he lied to the king.

However, the first lie was justified (albeit through the mouth of Abraham, not the narrator). That the second lie would not be explained to the reader at all seems jarring.

I guess another interpretation is based on something that other posters have asserted, that the words for "daughter" and "father" should be read loosely according to the languages spoken by the people involved. In that case, Sarah could have been Terah's grand-daughter; then maybe 11:31 left out this detail because the genealogies were being precise about lineage; while Abraham was being imprecise with Abimelech partly to cover up his first obfuscation. However, I would like to see where else in the Bible a granddaughter or grandson, for example, is referred to as a daughter or son.

Abraham just lacked faith at that time and was telling lies. He did not trust God to protect him, so he used his wife and her beauty instead – that's why God kept revealing and exposing him where ever he went.

In Ancient times, the word for "sister" also means "cousin" in Semitic languages. Aramaic word "Khtha" can mean sister or cousin. I believe the intended meaning here was Cousin.

Genesis 11:26-27 (NIV) - "After Terah had lived 70 years, he became the father of Abram, Nahor and Haran. This is the account of Terah’s family line. Terah became the father of Abram, Nahor and Haran."

If Sarai (later Sarah) was the daughter of Terah, then Sarai would have been listed along with Abram, Nahor, and Haran.

So we can confirm that the intended meaning was cousin.

In ancient Semitic languages, it must be noted that the word for father can also mean ancestor. For Example, Aramaic word "abba" can mean "father" or "ancestor/progenitor" (Source - Book "Introduction to Syriac" by Wheeler Thackston, Page 65)

Abraham was an Aramean (Deuteronomy 26:5) and Arameans spoke Aramaic. Abraham spoke Aramaic before he came to the land of Canaan where Old Hebrew was spoken. Laban the Aramean spoke Aramaic ("Jegar Sahadutha" in Genesis 31:47).

Check on Footnotes (at the bottom of the website) for "Jegar Sahadutha".

I also want to point out that the commandments were established as early as the time period when Noah lived. For Example, Noah knew about clean animals and unclean animals.

Genesis 7:2-4 - Take with you seven pairs of every kind of clean animal, a male and its mate, and one pair of every kind of unclean animal, a male and its mate, and also seven pairs of every kind of bird, male and female, to keep their various kinds alive throughout the earth. Seven days from now I will send rain on the earth for forty days and forty nights, and I will wipe from the face of the earth every living creature I have made.”

God gave Abraham commands, decrees, and instructions. Abraham obeyed God and kept all of what God taught him.

Genesis 26:4-5 - "I will make your descendants as numerous as the stars in the sky and will give them all these lands, and through your offspring all nations on earth will be blessed, because Abraham obeyed me and did everything I required of him, keeping my commands, my decrees and my instructions."

This is the same type of instruction God gave to Moses in Deuteronomy 11:1.

Deuteronomy 11:1 - "Love the Lord your God and keep his requirements, his decrees, his laws and his commands always."

But you may ask what about Moses' father marrying his aunt? In Hebrew Masoretic Text, it says this.

Exodus 6:20 (1917 JPS Tanakh English translation of Hebrew Masoretic Text) - "And Amram took him Jochebed his father’s sister to wife; and she bore him Aaron and Moses. And the years of the life of Amram were a hundred and thirty and seven years.“

This is confirmed as an error by Scholars, because Septuagint and Peshitta Tanakh (Aramaic Old Testament used in first century Israel) says Amram married his cousin.

Exodus 6:20 (Samuel Bagster & Sons' Translation from Septuagint) - "And Ambram took to wife Jochabed the daughter of his father's brother, and she bore to him both Aaron and Moses, and Mariam their sister; and the years of the life of Ambram were a hundred and thirty-two years."

Here is a link to check this information.

Exodus 6:20 (Lamsa translation of Peshitta Tanakh)- "And Amram took his uncle’s daughter Jokhaber, and she bore him Aaron, Moses, and Miriam; and the years of the life of Amram were a hundred and thirty-seven years."

But Peshitta Tanakh (Aramaic Old Testament) agrees with Hebrew Masoretic Text about Ambram’s age.

Cousin Marriage is permitted in the Bible. It is not in the prohibited marriage list mentioned in Leviticus Chapter 18. Aside from Exodus 6:20, we see cousin marriages in Genesis 29, Joshua 15:17, Numbers 36:1-11, 1 Chronicles 23:22.

During Abraham's time the law hadn't been written against a man taking his father's daughter as his wife. After the law was written in:

Deuteronomy 27:22 (NKJV)
²²  ‘Cursed is the one who lies with his sister, the daughter of his father or the daughter of his mother.’
“And all the people shall say, ‘Amen!’

it forbade such a practice even today, but the lineage of Christ was coming through Abraham and Sarah. This also shows what happens when we are faced with fear that our faith is too weak to overcome.

Marrying a close relative was not forbidden at that time. The old question of "Where did Cain get his wife?" is answered by saying that he married a sister of his. It was not immoral at that time, since there was no law forbidding it.

Leviticus is where we find such laws, which was written over 400 years after the time of Abraham. We now understand that as the genetic pool has become degraded, it is best not to marry a close relative because of the possibility of both husband and wife having the same genetic deficiencies.

Early on in human history, these genetic deficiencies were quite minimal, so there wasn't an issue.

Marrying a sister may have been uncommon at that time, so Abraham appears to be fudging a bit to justify Sarah as his sister. He has to explain how she is his sister, because she isn't his direct sister. So, he's trying to justify his lie by a tenuous explanation.

So again, there was no law that he was breaking at that time. It would be as if the government passed a law against eating twinkies and then rounded up everyone who had ever eaten one before it was outlawed. The American Justice system strictly forbids this practice (Ex Post Facto).