The Thanksgiving Loaves
When a Jew offered a todah thanksgiving sacrifice to G-d he was required to offer forty challot along with the animal, thirty of them consisting of three varieties of unleavened loaves and ten of them leavened. One of each ten challot went to the kohen performing the sacrificial service and the rest by the person bringing the sacrifices along with the flesh of the sacrificed animal.
What is the relationship between the animal itself and the challot accompanying it?
First of all, the moment the animal is slaughtered the challot acquire a sacred status and may be consumed only within the time and space limitation assigned to the flesh of the animal a day and night within the walls of Yerushalayim.
This is another aspect of the relationship between the todah sacrifice and the challot arising out of a nuance in a Torah passage. Should the kohen performing the sacrificial service intend, while performing one of its critical functions, that the flesh of the animal will be eaten on the following day rather than within the time limitation of a day and night stipulated by the Torah, he renders the flesh of that sacrifice pigul. Anyone subsequently consuming that flesh, even on the day that the sacrifice was offered, is guilty of a sin punishable by extirpation.
The improper intention which disqualifies the flesh by making it pigul also affects the challot even if no such intention related to them. This, explains Rabbi Kahana, is because the Torah refers to the challot as being an integral part of the todah sacrifice. Rather than instruct that the challot should be offered with the sacrifice the passage inversely states "he shall offer with the todah sacrifice challot" (Vayikra 7:12). This is a signal that the challot themselves are called todah and therefore share the same fate as the flesh of the sacrifice if an improper intention renders it pigul.
Who Can be a Shochet?
Although there are four critical functions in the sacrificial service which can determine the status of the sacrifice not all of them must be performed by a kohen. If the performer of the slaughtering, receiving of the blood, transporting it or applying it to the altar had an improper intention while carrying out his role he can disqualify the sacrifice in one of the degrees discussed in this mesechta and Mesechta Zevachim.
While the three functions beginning with the receiving of the blood in a sacred vessel must be performed by a kohen, the shechita slaughtering process may be performed by any Jew. Three sources are offered for this exception.
The first is the passage describing the offering of an olah sacrifice in which mention is made of the shechita of the animal followed by the requirement that "the kohanim, the sons of Aaron, will receive and apply the blood to the altar" (Vayikra 1:5). This is viewed as an indication that the role of the kohen begins only with the receiving of the blood, and that the shechita preceding that function may be performed by anyone.
Another signal comes from the proximity of that passage discussing shechita to the preceding passage requiring the owner of the animal being sacrificed to place his hands on its head before it is slaughtered in order to achieve his desired atonement (ibid. 1:4). The equation born of proximity leads us to the conclusion that just as any Jew can perform this function if he is the owner of the animal, so can any Jew also be the one performing the shechita.
A final source is found in the Torah instruction to the Kohen Gadol regarding the Yom Kippur service in the Beit Hamikdash. Moshe was told that Aaron must bring to this service a bullock of his own and that "he must slaughter the bullock sin offering belonging to him" (Vayikra 16:11). The insistence on the kohen doing the shechita in this case is an indication that in regard to all other sacrifices there is no need for a kohen and that every Jew is eligible to perform it.