The nakedness of thy sister,.... To lie with one in so near a relation is exceeding criminal, and for which the law curses a man, De 27:22; and to marry her is not lawful; for though it was necessary for the propagation of mankind that a man should marry his sister, for who else could Cain and Abel marry?
yet afterwards, when there was an increase of mankind, and there were people enough remote from each other, it became unlawful for persons in such near ties of consanguinity to marry with each other; though the Egyptians did, in imitation of Isis and Osiris , and so the Persians, following the example of Cambyses :the daughter of thy father, or the daughter of thy mother; whether she is a sister both by father and mother's side, or whether only by the fathers side and not the mother's, as Sarah was to Abraham, Ge 20:12; or only by the mother's side and not the father's:[whether she be] born at home or born abroad; not whether born and brought up in his and her father's house, or born and brought up in another place and province; though there were some, as Aben Ezra observes, that so interpreted it, according to the sense of the word in Ge 50:23; but rather the sense is, as that writer gives it, whether born according to the law of the house of Israel, after espousals and marriage, or without it; that is, whether begotten in lawful marriage or not, whether a legitimate offspring or spurious, born in adultery and whoredom, whether on the father or mother's side; so the Targum of Jonathan, whom thy father begat of another woman, or of thy mother, or whom thy mother bore or brought forth, of thy father, or of another man; and to the same purpose Onkelos:[even] their nakedness thou shalt not uncover; neither lie with, or have carnal knowledge of, nor marry one or the other.
Diodor. Sicul. l. 1. p. 23. Herodot. Thalia, sive, l. 3. c.