Deuteronomy 12:21

But if the place which the Lord your God will have chosen that His Shekinah may dwell there be too far off, then may you eat of your herds and flocks which the Lord your God shall give you, as I have com- manded you, in your cities you may eat, according to all the desire of your soul:

AND THOU SHALT SLAUGHTER etc. AS I HAVE COMMANDED THEE. The meaning thereof according to the opinion of our Rabbis is as follows: “As I have commanded thee — orally, by law declared to Moses on Sinai This teaches us that he was commanded with regard to [severing] the windpipe and the gullet, and [severing] the greater part of one [either the windpipe or the gullet] in a bird, and [severing] the greater part of both in an animal.”
Know that the term shechitah in the Sacred Language denotes the severing of the two organs in the neck [the windpipe and the gullet], and be not apprehensive because of what it says ‘vayishchateim’ (and He slew them) in the wilderness [which clearly does not signify severing the organs of the neck], for it is but a euphemism [as if to say] that He slaughtered them like sheep. Thus He commanded regarding the offerings, ‘v’shachat’ (and he shall slaughter), ‘v’shachatu’ (and they shall slaughter), which refer to the organs of the neck. Now at first [in the wilderness] He commanded that whatever [meat] they eat be of peace-offerings, that they be slaughtered according to the law of the offerings. Now, when he proceeded to permit the meat of unconsecrated animals, he said, and thou shalt slaughter of thy herd and of thy flock as I have commanded thee when such animals were brought as offerings, and you may eat them unconsecrated after all the desire of thy soul, meaning that He permits unconsecrated animals to be eaten everywhere, provided that they be slaughtered as He had commanded originally, when they were all [permitted only as] offerings. This is the correct meaning of the verse in line with the plain sense of Scripture. Perhaps our Rabbis intended this [thought] when they said in the Sifre: 75. “As I have commanded thee — just as the consecrated animals are slaughtered [in accordance with the traditional regulations] so must also the unconsecrated animals be slaughtered [with the same regulations].” Thus the commandment of slaughtering [animal and fowl] is here expressly stated and is explained in the words of our Rabbis on the basis of tradition.

כאשר צויתך, “as I have commanded you.” From the formulation, i.e. that G–d had given precise instructions, in this verse, our sages in the Talmud, tractate Chulin folio 28 derive the rule that when slaughtering a mammal both the major part of the gullet and the windpipe of the animal have to be severed. When slaughtering birds, the major part of the windpipe has to be severed. Rabbi Yaakov of Corveillle, found that the numerical value of the letters in the expression כאשר צויתך, equal the numerical value on the words: רוב אחד בעוף ורוב שנים בבהמה, “the major part of one for the bird, and the major part of two for the mammal.” (1047). [What the sages could do without the help of GOOGLE! Ed.] An alternate interpretation of this expression: The three letters in the word אשר, are אלף=1=אחד, for the א, 2 for the ש,=שנים, and the letter ר, short for the word רוב, “major part.”