Tosefta su Levitico 22:78

These are the signs in a [domesticated] animal [that render it permitted (Lev. 22:3)]: "In every animal with a hoof, a completely split hoof, [and that] chews its cud, such an animal you may eat." All those which chew their cud, they lack upper teeth. What ox grew horns before hoofs? This is the bull of Adam the First Man, as it says (Ps. 69:32), "That will please God more than oxen, [and more than] bulls with horns and hoofs." These are the signs in a wild animal: All that have horns and hoofs. Rabbi Dosa says, as long as it has horns, there is no need to inquire about hoofs. Even though there is no proof for this, there is at least a hint, [as it says,] "That will please God more than oxen, bulls with horns and hoofs." Rabban Shimon ben Gamaliel says, whatever has an extra claw in birds is clean [and] every bird that seizes its prey is unclean (see Hul. 3:6). Rabbi Shimon ben Elazar says, whatever grabs [its prey] in the air and does not have a gizzard that can be peeled [is unclean]. Rabbi Eliezer son of Tzadok says, when you place [a fowl] on a rope, if it divides [its claws] two in front and two in back, it is unclean. Others say, whatever [bird] dwells amongst the unclean [birds] or are similar [in appearance] to the unclean [birds] is unclean, [and] whatever [bird] dwells amongst the clean [birds] and is similar [in appearance] to the clean [birds] is clean. The relatives of the man (alt., "the people") from K'far Timarta that were in Judea would eat starlings (זרזירין, see Hul. 62a:2) because they have a crop of feathers. People from the upper marketplace in Jerusalem would eat the white sinonia because it had a gizzard that could be peeled.

One who slaughters an animal and finds inside it a living nine-month fetus, [the fetus] requires [ritual] slaughter, and it is liable for the gifts [of the shankbone, cheeks, and maw to the Kohen (Deut. 18:3)], and is forbidden under the laws of "it and its offspring you shall not slaughter in a single day" (Lev. 22:28), the words of Rabbi Meir. And the Sages say, It is not forbidden under the laws of "it and its young," as it says, "It and its young you shall not slaughter in a single day." That which requires slaughter is forbidden under the laws of "it and its young," but that which does not require slaughter is permitted under the laws of "it and its young," and exempt from the [priestly] gifts, as it says (Deut. 18:3), "from those that sacrifice the sacrifices." [Only] that which requires [ritual] sacrifice is liable in the [priestly] gifts. Rabbi Shimon Shezuri says, even if it is standing and ploughing over a furrow, one may tear it open and pour out its blood, cut it, and eat its flesh! Rabbi Shimon ben Elazar says in the name of Rabbi Yosei HaG'lili, [such an animal carries] the impurity of food-impurity, and imparts the impurity of food-impurity, and must be rendered fit [for eating]. Rebbi says, it does not impart the impurity of food-impurity because it is alive, and a living creature cannot impart the impurity of food-impurity.

"It and its young" (i.e., the prohibition against slaughtering a domesticated animal and its offspring on the same day, Lev. 22:28) applies to kilayim (i.e., a mixed-breed offspring whose parents are of different species) and to the k'vi (as to which the Sages were uncertain whether it was a domesticated or wild animal). Rabbi Eliezer says, this rule applies to a mixed-breed [offspring] of a ewe and a goat, but not to [a mixed-breed offspring whose parent is] a k'vi. One who slaughters "it and its young" as chullin inside [the Temple Courtyard] or as kodashim (a sacrificial offering) outside [the Temple Courtyard] [is liable]. One who slaughters a tereifah and so too one who slaughters [an animal] and discovers that it is a tereifah, Rabbi Meir forbids [slaughtering the parent or offspring of that animal] under the laws of "it and its young." The slaughter [of an animal] for medicinal purposes, as food for idolaters, or as food for dogs is forbidden under the laws of "it and its young." A deaf-mute, an imbecile, or a minor that slaughtered at a time that others were watching them, it is forbidden under the laws of "it and its young." [If] no one else was watching them, it is permitted under the laws of "it and its young." These are the words of Rabbi Meir. And the Sages say, in either case, the slaughter is forbidden, but if it was slaughtered, it is exempt. One who buys [an animal or its offspring] from the homeowner, he takes precedence over the homeowner [in slaughtering on that day] because he specifically bought it for that purpose. Two that bought a cow, the first purchaser [has the right to] slaughter first, but if the second slaughtered first, behold, he is rewarded for his alacrity. [If] he slaughtered it and its mother, even up to five generations, he is not liable but for one. [If he slaughtered it] and the daughter of its daughter, even up to five generations, he is liable on the last one. [If] he slaughtered and then someone else came and slaughtered [*the mother and someone else came and slaughtered] the daughter, the two last ones are liable, and the middle one (i.e., the one who slaughtered the "middle" generation) is exempt. [*Note: The bracketed text follows MS Vienna.] [If] he slaughtered five of her offspring he is liable as to all five for lashes (לַאו, see Jastrow). [If] he slaughtered five offspring and then slaughtered her, Summachos says in the name of Rabbi Meir, he is not liable but for one transgression. [If] he slaughtered her daughter and afterwards slaughtered her, and afterwards slaughtered her mother, the one who slaughtered the mother is liable and [the one who slaughtered] the daughter is exempt. [If the first] slaughter [occurred] before nightfall, it is permitted to slaughter her daughter at night. Once it becomes dark it is forbidden to slaughter her daughter the whole day and the whole night.

The precepts were given to Israel for no reason other than for Israel to stay alive, for it is said of the precept, "Which if a man do, he shall live by them" (Lev. 18:5) - live by them and not die by them. Therefore, when there is danger to life, no precept is to be insisted on except those prohibiting idolatry, unchastity, and murder. When does the rule apply? Not in a time of religious persecution. But during a time of religious persecution, a man must be willing to give up his life even for the least demanding of precepts, as it is said, "You shall not profane My Holy Name - I am to be hallowed among the children of Israel" (Lev. 22:32).

R. Aha said in the name of R. Akiva. Behold, it says: “If a thief is found tunneling in…” Is the house’s owner certain or uncertain? You must say he is uncertain. If they kill a person to save a life in a case of uncertainty, it is logical that they should push off the Sabbath, in order to save a life in a case of uncertainty. Behold, the commandments were only given to Israel that they might live by them, as it is written “Which a man shall perform and live by them” - he shall live by them, and not die by them. Nothing takes precedence over saving a life, save idolatry, sexual sins, and murder. In which circumstances are these things said? When it is not a time of persecution. But, when it is a time of persecution, even when it comes to the smallest of small commandments, a person should die for it, as it is written: “Do not profane my holy name” (Leviticus 22) and “the Lord made everything for his own sake” (Proverbs 16).