Zevachim, Chapter 2, Mishnah 1. In this chapter, the Mishnah lists a series of invalidations - factors that can occur during the service of an offering and invalidate it.
"Kol hazevachim shekibel daman zar":
A zar is someone who is not a kohen, and the service must specifically be performed by a kohen from the descendants of Aharon the kohen. The Mishnah begins specifically with "kibel" - receiving the blood into a service vessel, the sanctified vessel - and skips the first stage of the four blood services, the slaughtering, because the slaughtering is valid even if performed by a non-kohen. However, from the receiving and onward, including the conveying and the sprinkling, the service must be performed by a kohen, and if not - it is not valid but rather disqualified.
Continuation of the list of invalidations in the Mishnah:
Onen - A kohen who is in the intensive mourning period immediately following the passing of one of his seven relatives for whom he is obligated to mourn: father, mother, sister, brother, son, daughter, and wife. This refers to the day of death, and by rabbinic law, the ruling continues until the night after the burial, or for a period of one day until the burial of the relative. During this period, the kohen is not permitted to perform the service. It is worth noting that a Kohen Gadol serves even while being an onen, since he is forbidden to participate in the funeral anyway.
Tevul yom - One who was exposed to a source of tumah and immersed in a mikvah on that day, but whose sun has not yet set (nightfall), and therefore a remnant of tumah remains upon him. His status is that of a second-degree level of tumah: he may not eat Terumah, but he may eat things like maaser sheni. He is certainly not valid for the service, since any tumah, even in the smallest measure, invalidates the service.
Mechusar begadim - A kohen who is lacking his garments. The kohen must wear exactly four garments: the tunic, the trousers, the turban, and the sash (the fabric belt). Only these four, no less and no more: if he wore three out of four - he is invalid; if he wore two pairs of trousers - he is invalid. Even if he wore the four garments properly, if there is anything intervening between them and his flesh - such as tefillin of the arm placed on his arm under the tunic - the service is invalid. The garments must be exactly these four, directly on his flesh, without any addition. (As a side note: he is permitted to wear tefillin of the head on their own, since they do not interfere with the turban.)
The Kohen Gadol must wear all eight of his garments: to these four garments, he adds the tzitz (a sort of forehead plate upon which is written "Holy to God"), the choshen (a sort of breastplate), the ephod (apron), and the me'il (the robe woven with a checkered pattern and techelet dye). If he did not meet these requirements - his service is not valid.
Mechusar kippurim - The zav, the zavah, the woman after childbirth, and the metzora undergo a prolonged purification process, and at its conclusion they still lack atonement, as they are missing a specific offering. Until they bring it, their status is that of a third-degree level of tumah: they may eat even Terumah, but they may not eat consecrated items. A kohen who was a zav or a metzora, even though he was completely purified, waited all the required time, and immersed in a mikvah, does not return to the service until he brings his offerings, since until then a remnant of tumah remains in him - and any trace of tumah invalidates.
Shelo rachatz yadayim veraglayim - It is an obligation upon the kohen to wash his hands and his feet from the basin in the Courtyard prior to the service. The method of washing: he places his right hand on his right foot, and the water is poured upon them from the basin while he rubs, and similarly with his left hand and foot. If he did not wash properly - his service is invalid.
Arel - One who is uncircumcised. It is required that the kohen be circumcised, and even if according to halachah he is not obligated in circumcision - such as one whose older brothers died as a result of circumcision (like hemophiliacs), who is not circumcised lest he too die, Heaven forbid. Even though he must conduct himself this way and ends up uncircumcised against his will, he cannot perform the service, and if he served - he is invalid.
Tamei - Any tumah whatsoever invalidates the service. Seemingly there is no novelty here, since tevul yom and mechusar kippurim were already listed, which are the lightest levels; nevertheless, one who is tamei at any level is invalid from performing the service.
Yoshev - The kohen must stand during the service. If he sat on a chair or on the floor - he is invalid. Furthermore, he must stand completely barefoot, with his feet touching the floor of the Courtyard without any intervention.
"Al gabei keilim, al gabei behemah, al gabei raglei chaveiro":
One who stands on something else - whether on vessels, such as clothing, a pot, or a rug, whether on top of an animal, or whether on the feet of his barefoot fellow - is invalid, and this is not a valid service. These three stages progressively introduce novelties, one upon the other. The foundation of the matter: sometimes, even though an intervention is forbidden, if the intervening item is of the same kind (min bemino) - meaning, of the same type as the object with which contact must be made - it is not considered an intervention. For example, when taking the Four Species on Sukkot: many Ashkenazim hold the lulav using "koishlach", a lulav holder also made from the material of the lulav, and even though seemingly there is an intervention here - it is not an intervention, since it is of the same kind. Nevertheless, regarding a kohen, direct contact is required between his feet and the floor of the Courtyard, and therefore even one who stands on the feet of another kohen, which is somewhat of the same kind, is invalid. All the more so one who stands on an animal, and certainly on a vessel of any kind, a rug, shoes, and the like.
"Kibel bismolo":
Here the Mishnah transitions to a point of dispute, and to the matter of the blood itself: if he received the blood when the service vessel, the basin receiving the blood, was held in his left hand - he is invalid. This law is derived from a complex two-stage midrashic exposition, and all the invalidations listed here are based on verses and expositions. All the services of the kohen must be performed with the right hand.
"Rabbi Shimon machshir" - Rabbi Shimon rejects the exposition, or at least part of it, by virtue of his approach that "a verse is expounded based on what immediately precedes it and not on what precedes the preceding" - a technical matter that does not belong here. In his opinion, receiving the blood with the left hand is valid. In any event, the halachah follows the Tanna Kamma, that the service must be performed with the right hand.
Invalidations in the blood itself:
"Nishpach al haritzpah ve'asfo" - If the blood spilled on the floor and he gathered it from there, it is invalid. The blood must arrive directly from the neck of the animal into the sanctified service vessel for receiving. It is worth noting that if the blood was received properly in a service vessel and only afterward spilled on the floor, it would be possible to gather it again, but this is not the case that the Mishnah is discussing.
"Nesano al gabei hakeves" - if the blood was placed not on the altar, where it is supposed to be placed, but on the ramp going up to the altar, it is invalid. To understand the rest of the Mishnah, let us first explain the structure of the altar.
The structure of the altar:
The ramp is thirty-two amos long, and the altar itself has a base area of thirty-two by thirty-two amos (this is not the place for all the geometric details). The altar is built in three tiers:
The Yesod - the foundation, the bottom surface, thirty-two by thirty-two basically (although in practice it is more complex), one amah high.
The Sovev - the surrounding ledge, an additional five amos in height, going all around the altar.
The Ma'arachah - the top part where the fire burns, another three amos. Thus, one amah, plus five, plus three - a total of nine amos.
At the four corners protrude the horns, blocks of one amah by one amah by one amah, and as Rashi learns, from the top of the horn down to the floor below reaches ten amos.
The foundation below is visible from all four sides of the altar, but it does not surround everything equally. The two important directions in the Courtyard are the west and the north: as we recall, the altar was built in the northern part of the Courtyard, and we must also remember that one enters from the east and advances westward until the Holy of Holies is found in the far west - the Western Wall is the wall closest to the Holy of Holies. On the north and west sides, the foundation surrounds the altar along its entire length, whereas on the south and east sides, it extends for only one amah.
There is a requirement that the blood be placed on the wall of the altar, but in a place that has a foundation underneath it. Therefore, one who places blood on the southeastern horn, which does not have a foundation, has done nothing.
One must also know: at the midpoint of the altar's height, five amos from the ground, a red line called the Chut Hasikra goes around it, dividing its upper half from its lower half. Almost all types of blood must be placed on the lower part, below the Chut Hasikra, in order to be valid. The exception is the chatas, whose blood is placed on the four upper horns, above the Chut Hasikra.
Let us return to the language of the Mishnah:
"Nesano al gabei hakeves" - the ramp is not the altar, and therefore the placement is ineffective.
"Shelo k'neged hayesod" - the blood reached the wall of the altar itself, but not opposite a place that has a foundation underneath it, so it is ineffective.
"Nasan es hanitanin lematah lema'alah" - blood whose proper place is on the lower half, below the Chut Hasikra, such as the blood of an olah, and one threw it above the line, it is ineffective.
"Es hanitanin lema'alah lematah" - blood whose proper place is above the line, such as chatas blood, and one placed it below the line, it is ineffective. All of these are invalid.
"Es hanitanin bifnim bachutz":
As was said in the introduction, there are two altars. The inner altar stands in the Sanctuary, and it has three names: the Inner Altar, the Golden Altar, or the Incense Altar, and generally, the blood of sacrifices is not placed on it. It should be noted that there are five inner chataos that are offered there inside:
The two chatas offerings of Yom Kippur.
The par he'elem davar.
The special goat brought for idol worship.
The special bull brought for an anointed kohen in certain scenarios.
These are the unique and exceptional offerings that are offered inside; whereas the blood of all other offerings is placed on the outer altar, also called the altar of the olah or the copper altar, which was a vessel made of copper.
Therefore, blood whose place is inside but was placed outside - such as one of the inner chatas offerings of Yom Kippur, where one brought the goat designated for Hashem and placed its blood on the outer altar - is invalid, since it must be placed inside. And conversely, "hanitanin bachutz shenetanan bifnim" - those to be placed outside that he placed inside - the blood of a regular olah, asham, or shelamim whose place is on the outer altar, and he placed it on the inner altar - is invalid.
"Pasul ve'ein bo kareis" - it is invalid and does not carry the punishment of kareis: In all these cases, the offering is invalid, and therefore it is forbidden to eat its meat. Nevertheless, one who eats from the meat is not liable for the punishment of kareis, because the offering was not valid at all, and therefore this punishment does not apply to him.