Leviticus 18:7

The nakedness of thy father, or the nakedness of thy mother,
shall thou not uncover
By uncovering a father's nakedness is not meant anything similar to what befell Noah, which Ham beheld with pleasure, and the other two sons of Noah studiously and with reverence to their father covered; nor any sodomitical practice of a son with his father; as Gersom interprets it; but the same is meant by both phrases, and the words are by many interpreters thus rendered, "the nakedness of thy father, that is ^F24, the nakedness of thy mother thou shalt not uncover": for what is the mother's is the father's, and uncovering the one is uncovering the other; wherefore the mother only is made mention of in the next clause, where the reason of this prohibition is given: she [is] thy mother, thou shalt not uncover her nakedness;
that is, not lie with her, nor marry her, because she is his mother that bore him, of whom he was born, and therefore ought not to become his wife, or be taken into his bed; such a marriage must be incestuous and shocking; such were the marriages of Oedipus with his mother Jocasta, and of Nero with Agrippina; though the words will bear another sense, that a woman may not marry her father, which may be meant by the first clause, nor a man his mother, intended in the next; and where indeed it is not expressed, females in the same degree of relation are included with the males, and under the same prohibition; and so the Targum of Jonathan explains this, a woman shall not have to do with her father, nor a man with his mother; as Lot's two daughters had with him, and the Persians with their mothers; among whom such incestuous marriages and copulations were frequent, and especially among their Magi ^F25 who might not perform their office unless they had lain with their mothers, sisters, and daughters ^F26, or were begotten in such incest ^F1: a man guilty of such incestuous copulations was cursed by the law of Moses, ( Deuteronomy 27:20 ) ; this is contrary to nature, what the brute creation abhors; a camel will not cover its dam: Aristotle ^F2 reports of one who was betrayed into it by his keeper, who, after he had discovered it, fixed his teeth in him and slew him; and he also relates of a horse after that he had ignorantly done the same, ran away in great haste and cast himself down from a precipice headlong.