There is a dispute between Rav Nachman and Ameimar whether a bird possessing a single sign can be permitted if one is not expert in identifying the peres and ozniyah. Rav Nachman does not permit it, but Ameimar rules that any bird with a single sign is permitted, provided it is not known to be a predator (doreis), as there is no concern regarding the peres and ozniyah since they do not inhabit populated areas.

The characteristics of specific birds are defined, such as the white swallow (concerning which Rabbi Eliezer and the Sages disagree) and the sacrificial eligibility of birds like the tasil—which is valid before its maturity as a young dove (ben yona), but invalid if it has already reached maturity as a turtledove (tor).

Rav Asi enumerates eight birds whose status remains in doubt ("eight doubts") because their gizzards do not peel easily by hand but only with a knife. A series of short Amoraic traditions is presented, identifying various birds as forbidden or permitted and providing mnemonic signs to remember which of them are forbidden.

The Mishna states that the four physiological signs of a kosher bird are not explicitly detailed in the Torah, but are instead established by the Sages. The Gemara challenges this assertion based on a braita, which indicates that these kosher indicators are actually derived through a comparison of the anatomical details of each type of bird—specifically evaluating the characteristics of the nesher (griffin vulture), which is listed as non-kosher, against those of the tor (turtledove), which is known to be kosher due to its role in sacrificial offerings. Abaye resolves this difficulty by explaining that the analytical comparison of the physical details between the tor and the nesher outlined in the braita is precisely the methodology employed by the Sages to formulate and define these diagnostic signs.

Rabbi Chiya introduces a braita asserting that a bird possessing even a single kosher sign is permitted, based on the premise that only a bird structurally identical to the nesher—which lacks all four signs—is fundamentally excluded, along with the other non-kosher species explicitly enumerated in the Torah. The Gemara raises a difficulty, noting that one could argue the exact inverse: using the tor as the absolute paradigm, one could deduce that a bird is kosher only if it possesses all four signs. Since the other non-kosher birds listed in the Torah possess either one, two, or three kosher signs, the Gemara resolves the difficulty by explaining that if all four signs were universally required to render a bird kosher, there would be no logical necessity for the Torah to detail the other twenty-three non-kosher species, as their status as non-kosher would already be self-evident.

The Gemara then proceeds with a series of analytical queries, asking why the halakhic paradigm should not be derived from those forbidden birds that possess three signs, two signs, or one sign, respectively. In each instance, the Gemara answers using a redundant-case logic: if any of those categories served as the baseline paradigm, the Torah would have had no need to explicitly list the remaining forbidden species that possess fewer kosher signs (simanim).

The premise of the final query assumes that the peres and ozniyah (birds possessing a single kosher sign) could have established a binding paradigm were it not for the counter-example of the nesher. The Gemara immediately questions this, invoking the hermeneutical rule that two biblical verses teaching the same law cannot serve as a general paradigm (shnei ketuvim haba'im k'echad). Since both the peres and ozniyah share the same baseline characteristics, how could it be suggested that they form a general rule? The Gemara answers that they represent two distinct halakhic categories; one of them is completely unique because, within the entire biblical list of non-kosher birds, it is the sole species that possesses a specific, distinct kosher sign not found in any of the others.

In conclusion, the ultimate paradigm is the nesher (representing the principle that a bird is kosher unless it shares all the forbidden traits of the listed species), and we do not derive the rule from the tor. The tor (with all four kosher signs) is explicitly mentioned in the Torah solely to indicate its validity for sacrifices, rather than to serve as a universal archetype for kosher birds.

There is a series of theological debates between Rabbi Yehoshua ben Hananya and the Roman emperor, which demonstrate the sublimity of God through man's inability to look directly at the sun or to sustain the natural armies that serve God. A similar discussion with the emperor's daughter, who scoffed at the providence of God in the world, leads to a punishment of leprosy being inflicted upon her, emphasizing the principle that God's presence is indirectly guiding the world.

Rav Yehuda defines the difference between the dimensions of an ox and a donkey that affect the laws of buying and selling. He also explains that the ox sacrificed by Adam possessed only a single horn on its forehead, and that its horns preceded its hooves in creation. This structural precedence supports the view of Rabbi Yehoshua ben Levi, according to which all works of creation were created in their full stature, their full understanding, and their full mature form. Rabbi Chanina bar Papa expounds that the Angel of the World praised the grasses when they applied a kal v'chomer argument and proactively emerged according to their specific kinds (without intermixing), as derived from Genesis 1:11–12.

Rabbi Shimon ben Pazi reconciles the scriptural contradiction regarding the creation of the luminaries, detailing the moon's claim that two kings cannot share a single crown, which prompted the divine decree for it to diminish itself. To appease the moon, God granted it dominion by both day and night, linked Israel's calendar to the moon's counting of days and years, and called righteous people "small" like the moon. However, the moon was not appeased by all of these attempts, and God then established a sin offering to be offered on Rosh Chodesh (the New Moon) - a male goat - as an atonement for God. Rav Asi reconciles a contradiction in Creation regarding the emergence of vegetation, explaining that the grass remained hidden at the opening of the ground until the prayer of Adam brought down rain and caused them to sprout, teaching that God desires the prayers of the righteous.

Rav Chanan bar Rava identifies the shesua as a unique creature possessing two backs and two spinal columns - as definitive proof that the Torah is from Heaven, as it is impossible to believe that Moshe knew of the existence of that creature.

Reish Lakish analyzes a series of seemingly redundant verses, emphasizing that they constitute the core essentials of the Torah itself. For example, the description of the displacement of nations in the land of the Philistines and the land of Moab via intermediary conquests was legally meant to permit the eventual conquest of the land without violating ancient oaths or divine decrees.

Rav Yehuda discusses the physical dangers of consuming chiltit (asafoetida), particularly on an empty stomach, which Rav Yosef expands upon by listing other hazardous foods consumed on an empty stomach.

The Gemara notes that Rav initially permitted an animal whose legs had been severed because he verified that the convergence of sinews (tzumat hagidim) remained intact. Shmuel, however, cautioned him that the severing might have been caused by a venomous snakebite, rendering the animal forbidden due to mortal danger. Shmuel proposed a specific diagnostic test to detect the presence of venom; upon execution, the test confirmed Shmuel's suspicion that the injury was indeed the result of a snakebite.

The Mishna enumerates the physiological kosher signs for animals, birds, grasshoppers, and fish. A kosher mammal must possess fully split hooves and chew its cud. While explicit kosher signs for birds are absent from the Torah, the Sages established four indicators: a bird must not be predatory (dores), and it must possess an extra digit, a crop, and a gizzard with an easily peelable inner lining. Rabbi Elazar b'Rabbi Tzadok adds another sign, noting that a bird that evenly splits its digits when perched on a rope is definitively non-kosher. For fish, the required signs are fins and scales, though the Sages debate whether multiple scales are required or if a single scale suffices. Kosher grasshoppers must exhibit four specific traits: four legs, four wings, two extra jumping legs (kartzulayim), and wings that cover the majority of their body.

A braita asserts that any animal that chews its cud lacks upper front teeth. After addressing a series of difficulties regarding this rule, the Gemara clarifies that the absence of upper front teeth serves as a reliable indicator that an animal chews its cud and is kosher, with the sole exception of the camel (namely, a young camel). This anatomical indicator is practically valuable in cases where an animal's hooves have been severed, leaving no other means to determine its kosher status.

To differentiate between domesticated animals (behema) and wild animals (chaya) - a distinction crucial for determining the prohibition of forbidden fats (chelev), which applies exclusively to domesticated species - a braita states that a wild animal is identified by its horns and cloven hooves. The Sages debate whether the horn alone is a clear sign or if both criteria must be checked. To resolve the anomaly of the goat and an ox, which possess both traits yet are classified as domesticated, the Gemara explains that the horns of a wild animal must be either branched, or layered, grooved, and rounded.

The braita further notes that a single-horned animal, known as the keresh, is classified as a wild animal. This introduces a discussion regarding legendary creatures, specifically the keresh and the tigris. The Gemara recounts an incident where a Roman emperor requested that Rabbi Yehoshua ben Hananya show him the tigris. However, the creature's immense power caused widespread destruction from a distance, prompting the terrified emperor to beg Rabbi Yehoshua to return the beast to its place.

Conflicting traditions existed regarding Rav's ruling in the case of a dislocated femur in a bird. Ultimately, the analysis indicates that Rav permitted such a bird, except in regions where the prevailing custom was to forbid it. However, after presenting various differing opinions regarding this issue, which leaned primarily toward permissibility, the Gemara brings an incident demonstrating that the widespread, accepted custom was indeed to forbid this condition; consequently, the practical halakha is established to be stringent in accordance with this accepted communal custom.

Rav Huna defines a treifa as an animal that cannot survive for more than twelve months. A contradiction is raised against this definition from a braita that brings three alternative opinions regarding what legally constitutes a treifa, none of which align with Rav Huna's position. This difficulty is resolved by explaining that Rav Huna follows a different Tanna, whose view is reflected in another braita stating that one must wait through the winter months to determine whether an animal can successfully recover from its specific ailment.

The Mishna enumerates all the physical defects that cause a bird to be rendered a treifa, as well as those that leave it kosher. If a weasel (chulda) attacks a bird in an area where the brain membrane could have been perforated, the bird is considered a treifa. There are, however, different tests one can perform to ascertain whether the membrane was actually punctured, and the Gemara suggests various methods for this inspection. Conversely, in the case of birds that live in the water, a broken skull creates an absolute presumption that the brain membrane was punctured, meaning that no subsequent test will be effective in permitting the bird.

If a bird was caught in a fire and burned, the Gemara outlines specific ways to determine whether its internal organs were affected to the point of rendering the bird a treifa. This diagnostic procedure relies on checking for a change in color - either from red to green, or from green to red, depending on the specific internal organ being evaluated.

Following the Mishnaic list of kosher conditions in a bird that do not render it a treifa, the Amoraim introduce specific qualifications and limitations to restrict the scope of some of these permitted cases.

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Rava raises several difficulties against Rav Nachman's position that the term "until" implies up to but not including the final value. However, it concludes that the exact meaning depends on the specific context as one must always rule stringently with requisite amounts (shiurim), with the sole exception of a single requisite amount regarding the laws of niddah.

Regarding some of the cases enumerated as kosher in the Mishna (if the spleen and kidneys are removed, or the lungs shrivel up out of fear), the Sages qualify and restrict the specific parameters under which the animal is permitted.

Rabbi Meir and the Sages disagree regarding a skinned animal (geludah), where the skin has been entirely removed. Rabbi Shimon ben Elazar notes, however, that Rabbi Meir ultimately retracted his position and conceded to the view of the Sages.

Rav Bibi bar Abaye rules that although a standard hole in the windpipe requires the size of an issar (a coin), its clawing measurement (of redness) is a minimal amount, because the predator's venom burns and consumes the tissue continuously. Regarding the scope of the inspection required due to concern for venom, Rav Nachman testifies in the name of Rav that one must inspect from the base of the brain to the thigh, and not only adjacent to the intestines (as some hold). In an interesting story, Rabbi Yochanan defends the supreme authority of Rav against the queries of Reish Lakish, and consequently, Reish Lakish praises a different tradition of Rav, according to which an animal whose organs (simanim) were dislocated and was subsequently slaughtered is kosher.

It was established that new cases of treifot may not be added beyond those enumerated by the Sages, even if these injuries cause the death of the animal.

The Mishna enumerates structural defects that leave the animal kosher, including a windpipe that was perforated less than the size of an Italian issar, a brain membrane that was not punctured, and a liver of which a remains. This list gives rise to a fundamental dispute between Rabbi Yochanan and Reish Lakish regarding the scope of the lists in this chapter, which affects their approach to the ruling of Rav Matna, who rules that a femur bone that dislocated is a treifa. Rabbi Yochanan declares the animal kosher because the case was omitted from the exclusive list of treifot, while Reish Lakish rules it a treifa because it is absent from the exclusive list of kosher defects.

For the Babylonians, they defined that the size of the isser is similar to a Kurdish dinar, and the Gemara brings a story following this involving Rabbi Yochanan who went to a moneychanger looking for this coin,and told the moneychanger that craftsmen engaged in their work are legally exempt from standing before Torah scholars. How does this differ from craftsmen who would stand up and greet those Jews who were bringing their first fruits to the Temple?

Rav Nachman said that "up to an issar" it is not a treifa means up to but not including that size. Rava brings a series of difficulties against his view, but Rav Nachman answers them.

A cat or a weasel (chulda) renders a bird a treifa through clawing (derisa), whereas only a cat can do so for small cattle such as young goats and lambs. Other predatory birds besides those explicitly listed in the Mishna can also render other birds a treifa by clawing, but only when targeting birds smaller than themselves, while a hawk (netz) can do so even to birds of its own size. According to an alternate version, ordinary predatory birds can claw birds of their own size or smaller, whereas the hawk can even render birds larger than itself a treifa. Furthermore, two conflicting versions are presented regarding Rav Kahana's ruling in the name of Rav Shimi bar Ashi concerning foxes, debating whether or not they possess the capacity to render animals a treifa through clawing.

Abaye limits the laws of derisa to the predator's front legs, specifying that it must be executed specifically with a claw and not with teeth, must be done with intent, and must occur while the prey is still alive. In a case where a lion was found among oxen and a dislodged claw was subsequently discovered on the back of one of the oxen, Rabba bar Rav Huna ruled in the name of Rav that there is no concern for derisa. He reasoned that while most lions do claw, their claws do not generally detach in the process; thus, it is more probable that the ox rubbed against a wall and accidentally picked up a nail embedded there. The Gemara initially rejects this argument, countering that while oxen frequently rub against walls, nails rarely stick to their backs in this manner, and since the lion remains a viable source, one should rule stringently. Ultimately, the Gemara concludes that because the logic can support either side, the ox retains its presumptive status of permissibility; as a matter of pure doubt, Rav remains consistent with his opinion stated elsewhere that we rule leniently in cases of uncertain clawing. Abaye restricts this leniency, clarifying that it only applies when an actual claw is found embedded rather than a mere mark, when the claw is moist rather than dry, and when there are only one, two, or three claws scattered at random rather than two or three found in a distinct row.

Rav and Shmuel disagree on whether to rule leniently or stringently in cases of doubt regarding derisa. While both agree to rule leniently in certain scenarios, they dispute a case where a lion entered among oxen and the lion remained silent while the oxen were found bellowing in distress. Ameimar ruled stringently in accordance with Shmuel, either because he rejected Rav's view or because he believed Rav ultimately retracted his opinion, a shift suggested by a practical incident that occurred. Although several difficulties are raised regarding the specific details of that incident, they are successfully resolved. Rav Ashi similarly ruled leniently in a case of doubt.

If there is a doubt as to whether an animal was clawed, the Gemara rules that one may inspect the internal areas of the carcass to see if redness has formed from the venom; if no redness is present, the animal is permitted. This testing method was originally stated by the sons of Rabbi Chiya, though Rav Yosef pointed out that Shmuel himself had already articulated this principle. This discussion leads the Gemara to a series of inquiries - some regarding the laws of clawing and others concerning unrelated laws of treifot - all of which were concisely resolved by an authority who declared that each question had already been answered by a prior Rabbinic statement.

The Gemara discusses what other protective materials a bird could fall upon that would successfully cushion its impact and prevent it from being rendered a treifa. Relatedly, if a bird's wings become stuck to each other or to its body, a debate arises as to whether or not the bird will become a treifa upon falling, as its ability to break the fall is compromised. Two opinions are brought regarding the scope of this debate - specifically, whether the dispute applies to a case where only one wing is glued or if it is restricted to a case where both wings are glued.

The Mishna rules that if the majority of an animal's ribs are broken, it is a treifa. While there are twenty-six ribs total, consisting of thirteen on each side, two of these are excluded from the halakhic count; therefore, a majority is defined as twelve ribs, which can be comprised of six on each side or any other combination totaling twelve. Rav rules that even a single rib dislocated along with its socket from the vertebra renders the animal a treifa. Rav Asi and Rav Kahana then questioned Rav regarding a case where two opposite ribs are completely removed while the vertebra remains intact, to which Rav responded that it is a neveila because the animal is essentially cut in half. Several questions are raised against this response in light of Rav's own previous statement, wondering why they would ask about two ribs if Rav already held that even one dislocated rib is a treifa. Ultimately, the Gemara resolves this by reinterpreting the precise details of their question and explaining that they were unaware of Rav's original ruling when they questioned him.

Three of the seven extra cases of treifot introduced by the Amoraim were authored by Shmuel and are analyzed here because one of them directly relates to uprooted ribs.

The next case in the Mishna transitions to an attack by a predator animal that emits venom (derisa), creating a treifa status. At first, a statement of Rav is brought asserting that a cat does not emit venom capable of making an animal a treifa, prompting the Gemara to question why this rule could not be inferred directly from the wording of the Mishna itself. Rav Chisda rules that a cat and a mongoose do emit venom that can kill a small kid or a baby lamb. A contradictory braita is brought against this view, and the contradiction is ultimately resolved in two possible manners.