“When HaShem your Lord enlarges your borders as He has promised you [and you live far away from the Beis HaMikdash and you cannot partake of the meat of the Korbonos] and you say, ‘I would like to eat meat [without bringing a Korbon]!’ — Yes, you may eat meat as much as you like, and since the holy place that HaShem will choose to be His Beis HaMikdash is far away, therefore you shall slaughter of your cattle and sheep which HaShem has given you, in the manner that I have commanded you, and eat meat in your towns however you like.”
Devorrim, 12 : 20 — 21
“You shall slaughter ... in the manner that I have commanded you ...” If you search from ‘In the beginning’ to ‘in full view of all the Jewish People’ [that is, from the first word of the Torah to the last] you will not find another word about how to slaughter. Yet Mosheh our Teacher says here, “You shall slaughter ... in the manner that I have commanded you”! Where? In Tractate Chullin (where all the laws of Shechita are taught)! Indeed, we have learned in a Beraisoh: Rabbi [Yehudah the Prince] says: ‘You shall slaughter ... in the manner that I have commanded you ...’ — this Possuk teaches that when he was on Mount Sinai, Mosheh was instructed by HaShem Himself [in all the laws of Shechita] and all this was taught to the Jewish People by Mosheh.
Babylonian Talmud, Tractate Chullin, 28a and Rashi
The commandment concerning Shechita is that whoever wants to eat the meat of a kosher species of domestic animal, or of kosher animals of the wild or the meat of any kosher fowl, must first slaughter these creatures properly and it is permitted to eat the meat of any of these only if they have been slaughtered correctly. It is concerning this commandment that the Torah says, “You shall slaughter of your cattle and your sheep ... as I have commanded you.” ... The Mitzvah applies in every place and at all times, to males and females ... The reason for this commandment of Shechita, including that the Shechita knife must be exceedingly sharp and that it must be checked a number of times to ensure that there is not even the slightest nick or dullness, and exactly where on the throat the Shechita must be done, and the five main invalidators of a kosher Shechita — all these things are because of the prohibition of causing unnecessary pain to any creature for the consensus is that the prohibition of causing unnecessary pain to any creature is forbidden by Scripture itself. Slaughtering at the throat with an exceedingly sharp Shechita-knife is to minimize the pain of the creature because slaughtering at the
