Midrash su Levitico 11:46

5) (Vayikra 11:46): "This is the law of the beast and the bird": In which law is the beast similar to the bird, and birds, to the beast? A beast confers tumah by being touched or being carried, and a bird does not confer tumah by being touched or being carried, (but only by being eaten)! A bird confers tumah upon one's clothing (if another stuffs it) into his esophagus; and not, a beast! In which law, then, is the beast similar to the bird, and the bird, to the beast? We are hereby being taught that just as a beast (is slaughtered) by shechitah, so birds (are slaughtered) by shechitah. — If so, (why not say, then, that) just as a beast required two (shechitah) signs (to be severed), so, a bird, requires two, or the greater part of two? It is, therefore, written "This" (i.e., only in this respect (shechitah in general) that they are similar, but not in the other). R. Elazar says: In which law is a beast similar to a bird, and a bird to a beast? To teach us that both (are rendered fit) through the throat. — If so, (why not say, then, that) just as a bird (is "pinched") opposite its nape (viz. Vayikra 5:8), so a beast, opposite its nape; it is, therefore, written (Vayikra 5:8) "its head" — the head of a bird opposite its nape, and not the head of a beast.

6) "… and of every living creature that swarms in the water": (as requiring "distinguishing" [viz. Vayikra 5:47]). "and of every creature that creeps on the earth": including grasshoppers. And what is the nature of this "distinguishing" ("havdalah")? It is not enough to learn about them, but one must have perfect "recognition" of which (of them) are unclean and which are clean.

"A woman when she gives seed (conceives)" [Leviticus 12:2]: That's what is written, "You have created me behind and before." [Psalms 139:5] Said Rabbi Yochanan: If man merits, he inherits two worlds, this one and the coming one, that's what is written: "You have created me behind and before (front)." And if not, he comes to give reckoning, as it says, "And You laid your hand (kapcha) on me." [ibid], as it is written, [Job 13:21] "Withdraw your hand (kapcha) far from me." Said Rav Shmuel bar Nachman: When the Holy One, blessed be He, created the first man, he created him as an androgynous being. Reish Lakish: When it was created, dual faces [together] were created, and it was cut, and two were made. [One] back was male, [one] back was female. They challenged him: [Genesis 2:21] "And He took one of his ribs (tzela)"!? He said to them, it is of his sides, as it is written, "and to the side (tzela) of the Tabernacle" [Exodus 26:20]. Said Rabbi Berachiya and Rabbi Chelbo and Rabbi Shmuel bar Nachman: When God created the first man, from one end of the world to the other end, He created him to fill the entire world. How do we know from east to west? As it says, "You created me back to east (kedem)." How do we know from north to south? As it says, [Deuteronomy 4:32] "From the ends of the heavens to the ends of the heavens." How do we know that it was the expanse of the world? As it says, "And You laid your hand on me." Said Rabbi Elazar: "Behind" - that's the first day [of creation]. "Before" - that's the last day. For the opinion of Rabbi Elazar, there is the verse, [Genesis 1:24]: "Let the earth bring forth the living soul (nefesh chaya) to its kind." "Living soul" - that's the spirit of the first man. Said Reish Lakish: "Behind" - that's the last day. "Before" - that's the first day. For the opinion of Reish Lakish, there is the verse: [Genesis 1:2] "And the spirit of God wavered upon the water" - that is the spirit of the king messiah. If man merits, we say to him: "You were created before all of creation." If not, we say to him, "The mosquito preceded you." Said Rabbi Yishmale b'Rabbi Tanchum: "Behind" on all creation, "before" (first) in all punishments. Said Rabbi Yochanan: Even man's praise only comes last, as it says [Psalms 148:110]: "Beasts and all cattle creeping things and flying fowl". And afterwards, [Psalms 148:11]: "Kings of the earth and all peoples." Said Rabbi Simlai: "Just like man's formation was after beast, cattle, and bird, so too his laws are after beast, cattle, and bird, and that's what is written, "This is the law of cattle" [Leviticus 11:46], and afterwards, "A woman when she gives seed..."