Weren't Abraham and Sarah in an incestuous marriage?
Wasn't this marriage approved and blessed by God?
King James Bible
And yet indeed she is my sister; she is the daughter of my father, but not the daughter of my mother; and she became my wife.
Same Father not same mother.
The laws did not exist in the time of Abraham (Abram) and Sarah (Sara).
So they did not have an incestuous marriage because there was no law about those things at that time.
Leviticus 18:8-18King James Version (KJV)
8 The nakedness of thy father's wife shalt thou not uncover: it is thy father's nakedness.
9 The nakedness of thy sister, the daughter of thy father, or daughter of thy mother, whether she be born at home, or born abroad, even their nakedness thou shalt not uncover.
10 The nakedness of thy son's daughter, or of thy daughter's daughter, even their nakedness thou shalt not uncover: for theirs is thine own nakedness.
11 The nakedness of thy father's wife's daughter, begotten of thy father, she is thy sister, thou shalt not uncover her nakedness.
12 Thou shalt not uncover the nakedness of thy father's sister: she is thy father's near kinswoman.
13 Thou shalt not uncover the nakedness of thy mother's sister: for she is thy mother's near kinswoman.
14 Thou shalt not uncover the nakedness of thy father's brother, thou shalt not approach to his wife: she is thine aunt.
15 Thou shalt not uncover the nakedness of thy daughter in law: she is thy son's wife; thou shalt not uncover her nakedness.
16 Thou shalt not uncover the nakedness of thy brother's wife: it is thy brother's nakedness.
17 Thou shalt not uncover the nakedness of a woman and her daughter, neither shalt thou take her son's daughter, or her daughter's daughter, to uncover her nakedness; for they are her near kinswomen: it is wickedness.
18 Neither shalt thou take a wife to her sister, to vex her, to uncover her nakedness, beside the other in her life time.In fact it was God who made it all stop by telling them not to do the things they once did. It is like the fall, Adam could not die till he had sinned. Before the fall he had the right to eat of any tree including the tree of life.
9 And out of the ground made the Lord God to grow every tree that is pleasant to the sight, and good for food; the tree of life also in the midst of the garden, and the tree of knowledge of good and evil.
16 And the Lord God commanded the man, saying, Of every tree of the garden thou mayest freely eat:
17 But of the tree of the knowledge of good and evil, thou shalt not eat of it: for in the day that thou eatest thereof thou shalt surely die.
after the fall:-
22 And the Lord God said, Behold, the man is become as one of us, to know good and evil: and now, lest he put forth his hand, and take also of the tree of life, and eat, and live for ever:
23 Therefore the Lord God sent him forth from the garden of Eden, to till the ground from whence he was taken.
24 So he drove out the man; and he placed at the east of the garden of Eden Cherubims, and a flaming sword which turned every way, to keep the way of the tree of life.
Had man not eaten from the tree of knowledge of Good and Evil, he would never have known if he had done any wrong.
But now he knew and in his fallen state he could not eat from the tree of life.
Abraham could not be guilty of incest as there was no law or knowledge it was wrong in his time.
Intermarriage happened everywhere. But when God brought the laws to his people then it stopped and it then became wrong.
Once they had the knowledge they could no longer do those things...
