Halakhah su Levitico 11:4

Whether or not there is a specific midrashic reference to a pig which chews the cud, it would appear that an animal which has split hoofs and which also chews its cud is ipso facto kosher. Indeed, Jewish law does not even deem it essential to examine an animal for the manifestation of both split hoofs and the chewing of the cud. Leviticus 11:4-6 enumerates three species of ruminants which chew the cud but which do not have split hoofs: the camel, the rock-badger and the hare. Deuteronomy 14:7 names a fourth animal, the shesu'ah, which is described as chewing the cud but as not having cloven hoofs. This animal is described by the Gemara, Hullin 60b, as a creature which has two backs and two spinal columns. The Gemara, Niddah 24a, further explains that the shesu'ah is the progeny of a permitted species. In effect, the birth of a shesu'ah is an anomaly. Both Leviticus 11:7 and Deuteronomy 14:8 name only one animal, the swine, which has split hoofs but does not chew its cud. The Gemara, Hullin 59a, on the basis of a pleonasm, regards these enumerated species, not as paradigmatic, but as exhaustive. Thus the Gemara comments, "The Ruler of the universe knows that there is no other beast that chews the cud and is unclean except the camel [and the other species enumerated by Scripture]" and similarly comments, "The Ruler of the universe knows that there is no other beast that parts the hoof and is unclean except the swine." These dicta pave the way for a determination that an animal may be declared kosher even without examination for the presence of both split hoofs and the chewing of the cud. The Gemara, Hullin 59a, notes that the absence of upper incisors and canines is a characteristic of all ruminants with the exception of the camel which has canines in both jaws.²²The front teeth in the upper jaw of ruminants are replaced by a horny pad. The front teeth of the lower jaw are directed forward and, upon closing the mouth, simply press the grass tightly against this pad. When the head is jerked sideways the gum is cut through by the sharp edges of the lower front teeth. See Encyclopedia Britannica (Chicago, 1966), XIX, 752. Accordingly, declares the Gemara, "If a man was walking in the desert and found an animal with its hoofs cut off, he should examine the mouth; if it has no upper teeth he may be certain that it is clean, otherwise he may be certain that it is unclean; provided, however, … he recognizes the young camel." The possibility that the animal may be a young camel must be excluded since, even though the young camel has no teeth, it will eventually develop canines. The Gemara explicitly negates the possibility that there may exist some other animal that lacks teeth, i.e., a ruminant that chews the cud but is non-kosher by virtue of its non-cloven hoofs. Thus, if it were to be shown that the babirusa lacks incisors and canines on its upper jaw it may be declared a kosher species on that basis alone. Absence of incisors and canines is itself evidence that the animal is a cud-chewing ruminant.

That is that He commanded us to check for the signs of beasts and animals that can be slaughtered - and that is that they chew the cud and have split hooves - and it is then permissible to eat them. And in that we are commended to check them for these signs, it is a positive commandment. And that is His, may He be blessed, saying, "These are the animals that you may eat" (Leviticus 11:2). And the language of the [Sifra] (Sifra, Chapter 3:1) is, "'Such may you eat' (Leviticus 11:3) - it may be eaten, but an unclean beast may not be eaten." This means to say, a beast that has these signs is permissible to eat; so it indicates that a beast that does not have these signs is not permitted to eat. And this is a negative commandment that is derived from a positive commandment - which is a positive commandment, as is a principle with us. And therefore, it said after this statement, "This tells me only of a positive commandment. From where [do we know that he also transgresses] a negative commandment? [Hence] we learn to say, 'the camel, etc.'"(Leviticus 11:4) - as I will explain in the Negative Commandments (Sefer HaMitzvot, Negative Commandments 172). Behold it has already been made clear that His saying, "such may you eat," is a positive commandment. And the content of this commandment is that we are commanded to check for these signs in the beasts and animals; and it is not permissible to eat them without this. And this law is the commandment. And the regulations of this commandment have already been explained in Tractate Chullin and in Bekhorot. (See Parashat Shemini; Mishneh Torah, Forbidden Foods 2.)

To not eat an impure beast or animal: To not eat an impure beast or animal, as it is stated (Leviticus 11:4), "this shall you not eat from those that bring up the cud and separate their hoof, the camel," "and the pig" (Leviticus 11:7), "and the hare" (Leviticus 11:6), "and the daman" (Leviticus 11:5). And a clear negative commandment about the other species of impure beasts does not appear. But since the Torah stated (Leviticus 11:3), "All that separate the hoof and [...] bring up the cud in an animal, it shall you eat," we know that we are prevented from eating anything that does not have these two signs together. And this is a negative commandment that comes from the implication of a positive commandment. And the principle that we have is [that] a negative commandment that comes from the implication of a positive commandment, is a positive commandment, and [so] we do not administer lashes for it.