Zevachim Chapter 7, Mishnah 5. We return to the topic of tumas beis habliyah - the tumah conveyed by the carcass of a pure, kosher bird, such as turtledoves and young pigeons that are fit to be brought as an offering in the Beis Hamikdash. We will start with an introduction: Shechitah, which is the standard method, accomplishes two separate things - it renders the animal fit to be eaten according to halachah, and it also saves it from becoming a nevelah that conveys tumah. These two points are independent of each other: An animal that has undergone a valid shechitah is not a nevelah, and nevertheless, it might still be forbidden to eat - for example, if a tereifah is found in its intestines.
This exact same principle applies to melikah. Regarding the melikah of a bird in the Beis Hamikdash, we must distinguish between three matters:
Rendering it fit to be offered as a korban.
Rendering it fit for the kohanim to eat.
Saving it from becoming a nevelah that conveys tumah.
The Mishnah clarifies when melikah is ineffective at rendering the bird fit for offering or eating, and yet it is effective at preventing it from becoming a nevelah.
Four cases that do not convey tumas beis habliyah:
"Malak b'smol" - The kohen performed melikah with his left hand. This is invalid, and the bird is forbidden for offering and eating; but since the act of melikah itself was performed correctly from a technical standpoint, it is a valid melikah and does not convey tumah.
"O balaylah" - The Temple service must be performed during the day, and melikah performed at night is invalid. Nevertheless, it is a melikah, and it does not convey tumah.
"Shachat chullin bifnim" - A person took a non-sacred chicken and slaughtered it with a knife inside the Temple courtyard. This is forbidden, but the shechitah takes effect and it is not a nevelah, even though a forbidden act was done with it.
"V'kodashim bachutz" - He slaughtered a consecrated offering outside the Beis Hamikdash. This is also forbidden, but the shechitah takes effect and is effective at preventing the bird from becoming a source of tumah.
In all four of these cases, the Mishnah states: "Einan metamin b'veis habliyah" - They do not convey tumah in the esophagus. Even though it is forbidden to eat them, one who eats them does not become tamei.
The cases that convey tumas beis habliyah:
"Malak basakin" - He pierced the back of the neck and cut one or two of the signs, but instead of using his fingernail, he used a knife. Melikah requires the body of the kohen, and therefore this is not a melikah at all, but rather merely mutilating the animal. It is a nevelah, and one who eats it becomes tamei, aside from the prohibition of eating it.
"Malak chullin bifnim" - He took a non-sacred chicken and performed melikah on it in the Beis Hamikdash. One might have thought that in the Temple one can perform melikah instead of shechitah, but this is not the case: Chullin require shechitah everywhere. It turns out that this is nothing but mutilating the chicken by piercing its neck with a fingernail and killing it, and it is a nevelah that conveys tumah, and it is not even fit to be eaten since it was not slaughtered.
"V'kodashim bachutz" - He took a consecrated bird outside the Beis Hamikdash and performed melikah on it there. Melikah is only valid in the Temple, and there is no slaughtering of consecrated items outside; it turns out that this is nothing but destroying the bird, and it conveys tumah.
"Hatorim shelo higia zemanan" - Among the birds that are kosher for offerings, there are two types: Turtledoves, which are fit when they are mature, and young pigeons, which are fit when they are young. A turtledove that has not reached maturity - and the sign of maturity is that its feathers begin to turn yellow (we will deal with the details of the signs on another occasion) - is invalid for an offering, and performing melikah on it is merely an act of destruction, and it is a nevelah that conveys tumah.
"U'vnei yonah she'avar zemanan" - Young pigeons that have reached maturity and whose feathers have turned yellow are no longer offered. One who performs melikah on them is merely destroying a bird, and it is a nevelah that conveys tumah.
"V'shibesh gapah" - Simply put, its wing is damaged. Minor blemishes that disqualify cattle and sheep do not disqualify birds, because of their small size, and we do not scrutinize them; but prominent, clearly visible blemishes disqualify them from being an offering. A bird whose wing is broken and dysfunctional - even if it has not been detached from its body - is blemished and invalid, and performing melikah on it is merely destroying an animal and rendering it a nevelah.
"V'shenismis einah" - This does not mean mere blindness, which is not a blemish, but that the eye has been uprooted from its place. It is a major blemish and disqualifies the bird, and performing melikah on it renders it a nevelah.
"V'shenikte'ah raglah" - Its leg was cut off, and this too is a major blemish that disqualifies it for an offering. One who performs melikah on it is merely acting destructively, and the bird becomes a nevelah that conveys tumah when eaten.
In all of these, the Mishnah states: "Mitamei b'veis habliyah" - It conveys tumah in the esophagus. These are simply fundamentally invalid methods of melikah, the bird was not properly slaughtered, and it is therefore a nevelah that conveys tumah to the one who eats it at the moment it goes down the esophagus.
The rule established by the Mishnah:
The Mishnah establishes a guiding rule. It does not encompass all the cases, but it applies to many of them:
"Kol shehayah pesulah bakodesh - ein metamei beis habliyah" - any bird whose disqualification occurred in the Sanctuary does not transmit tumah in the esophagus. This refers to a bird that was inherently fit to be offered and was brought properly to the Beis Hamikdash, but the disqualification occurred during the service itself, such as if the kohen performed melikah (nipping the neck) with his left hand, and the like. As long as the act was performed correctly from a technical standpoint - with the thumbnail, at the back of the neck, and severing the required number of simanim (the windpipe and esophagus) - it is considered melikah, and it saves the bird from the status of neveilah (an unslaughtered carcass) even though it is not valid as an offering.
"Lo hayah pesulah bakodesh - metamei b'veis habliyah" - if its disqualification did not occur in the Sanctuary, it transmits tumah in the esophagus. This refers to a bird whose disqualification was not generated during the service but preceded it, so that it was not fit for melikah from the outset, such as a bird whose time had not yet come or whose leg was severed. In these cases, the melikah is not considered a Temple service at all, but mere crushing, and the bird is a neveilah: one who eats it violates a prohibition and even contracts tumah in the esophagus.
Melikah Performed by Those Disqualified for the Service:
The Mishnah adds another group of cases: "Vechol hapesulim" - and all those disqualified for the service. This refers to a zar (non-kohen), a tamei kohen, an onen kohen, and the like, who have no business performing melikah. If they performed melikah, their melikah is invalid in terms of the Temple service and the offering is not offered on the Altar. However, since the bird itself was fit for melikah and the act was performed correctly, it is an invalid melikah and not an invalid shechitah, and it does not transmit tumah in the esophagus.
In summary: In this Mishnah, we learned to distinguish between the validity of the offering and its fitness for eating, and saving the bird from the tumah of a neveilah. A disqualification that was generated during the service - whether due to the location, the timing, or the kohen performing it - does not remove the status of melikah, and therefore the bird does not transmit tumah in the esophagus. On the other hand, a disqualification that preceded the service, whether in the bird's body (its timing or its blemishes) or in the form of the act (melikah with a knife or melikah of a non-sacred bird), completely nullifies the status of melikah, and the bird becomes a neveilah that transmits tumah to the one eating it in the esophagus.