Halakhah sa Genesis 20:12: Mishneh Torah, Kings and Wars

Six are forbidden to the non-Jew⁸⁹With whom he may not engage in sexual relations.: 1) his mother, 2) his father’s wife, 3) a married woman, 4) his maternal sister, 5) a male, and 6) an animal. From “and so a man will leave his father” (Genesis 2:24), we learn of the prohibition with his father’s wife; “and his mother” (ibid.) – this is learned in its literal sense; from “and cleave to his wife” (ibid.) we deduce - and not his friend’s wife; from “his wife⁹⁰Or, his woman.” (ibid.) - and not with a male; from “and they shall be as one flesh” (ibid.) - we learn about the animal or beast or bird since he and they are not of the same flesh; and it says, “she is indeed my sister the daughter of my father, but not the daughter of my mother. And so she became my wife.” (Genesis 20:12).