Midrasch zu Wajikra 10:11

9) (Vayikra 10:10) "so that you distinguish between the holy and the profane": This refers to (inebriation as disqualifying one for) valuations (of animals dedicated to the sanctuary), allotments (for sacred use), and Temple dedications; "and between the unclean and the clean": This refers to (rulings in matters of) uncleanliness and cleanliness; (Vayikra 10:11): "and to teach the children of Israel": These are the teachings (of what is forbidden and what is permitted); "all the statutes": These are the expoundings (of halachoth); "that the L–rd spoke to them": These are the halachoth (spoken to us by Moses but not written in the Torah); "by the hand of Moses": This is Gemara. I might think that it is also forbidden to teach Mishnah (after drinking); it is, therefore, written "and to teach" (halachah), (excluding Mishnah, from which halachah is not taught.)

9) (Vayikra 20:11) ("And a man who lies with his father's wife, he has revealed the nakedness of his father. Both of them shall be put to death; their blood is in them.") "And a man": to exclude a minor. "who lies with his father's wife": This implies both his father's wife who is his mother and his father's wife who is not his mother. Whence do we derive (for inclusion) his mother who is not his father's wife, (as when his father raped a woman, who gave birth to him)? From "he has revealed the nakedness of his father," which is superfluous for (purposes of) comparison and the derivation of an identity (gezeirah shavah [below]). "Both of them shall be put to death": by stoning. You say by stoning, but perhaps it is by one of the other death penalties in the Torah! It is, therefore, written "their blood is in them" and, elsewhere (Vayikra 20:27) "their blood is in them." Just as the penalty there is stoning; here, too, it is stoning. We have heard the punishment, but we have not heard the exhortation. It is, therefore, written (Vayikra 18:7) "The nakedness of your father and the nakedness of your mother you shall not reveal." "the nakedness of your father" — this is your father's wife. You say that it is your father's wife, but perhaps it is your father's nakedness, literally, (i.e., sodomy)! — You reason (otherwise), viz.: It is written here (Vayikra 18:7) "the nakedness of your father," and elsewhere (Vayikra 20:11) "he has revealed the nakedness of his father." Just as "the nakedness of his father there refers to the wife of your father, so "the nakedness of your father" here (Vayikra 18:7) refers to the wife of your father, and it implies both the wife of his father who is his mother and the wife of his father who is not his mother. Whence is derived (for inclusion) his mother who is not the wife of his father, (but a woman he ravished)? From (Vayikra 18:7) "the nakedness of your mother you shall not reveal." This tells me only of the exhortations. Whence are the punishments derived? You derive it by induction, viz.: It is written here (Vayikra 18:7) of the nakedness of his father, and it is written elsewhere (Vayikra 10:11) of the nakedness of his father. Just as in the latter instance, his mother who is not the wife of his father, (but a woman he ravished) is equated with his father's wife, in the former instance, too, she is equated with his father's wife, (and this is the "gezeirah shavah" referred to above). (Vayikra 18:7) "she is your mother": You make him liable for (only one sin-offering, by reason of her being) his mother, and you do not make him liable for (another sin-offering, by reason of her being) his father's wife.