This week’s parshah contains the source for the halacha of following the rov (majority). The pasuk states: “acharei rabbim lehatos.” The Gemara in Chullin 11a says that this pasuk is referring to the Sanhedrin where the halacha follows the majority opinion of the judges. Similarly this applies to a case in which someone found a piece of meat that could have only come from one of ten stores – nine of which are kosher and one which is not. Such a piece of meat is permitted mi’de’oraisa since we can assume that it came from one of the majority of kosher stores.
The Gemara in Chullin (ibid.) says that there are two types of rov. One is the one described in the two aforementioned cases of judges and kosher stores. This type of rov is known as ruba d’eissa kaman – all the possibilities are in front of us.
The other type of rov is a ruba d’lessa kaman, whereby the options are not in front of us but rather based on a natural tendency, e.g. the majority of animals are not treifos. We do not have all the animals in front of us knowing that a certain number of them are kosher and thus many are non-kosher. We simply know that animals are generally kosher and not treifos.
It is this rov that we rely on every time we eat a piece of meat or poultry. There are eighteen different treifos in an animal that can render it treifa. However, checking for all of them would be extremely tedious and timely. Therefore the halacha mi’de’oraisa is that we do not check them but instead rely on the rov, and posit that this animal is from the majority of animals that are not treifos. There is one exception: the lungs. Since it is more common for the lungs to become treifa, albeit a majority is still kosher, we check the animal’s lungs to see whether it is treif.
The Gemara in Chullin (ibid.) asks: Where is the source for the halacha that we follow this rov? The Gemara makes many attempts to cite sources, some disproved and others holding up. The Gemara concludes that it must be that the Torah allowed us to follow this type of rov, for, if not, how can we eat the korban Pesach and other korbanos that must be eaten? The Gemara thus remarks that in cases where it is necessary, we can follow the rov – and where it is not, we do not have a source.
Rashi there says that even though the Gemara does not have a source, the halacha is that we may follow such a rov even in cases where it is not necessary. He cites two sources for this: One is that it is a halacha l’Moshe mi’Sinai. The other is that we derive it from ruba d’eissa kaman.
A question is asked on Rashi’s second cited source. It was clear to the Gemara that we could not simply derive ruba d’lessa kaman from ruba d’eissa kaman. It was for this reason that the Gemara expended a lengthy effort in citing numerous other sources. How can Rashi say that we derive ruba d’lessa kaman from ruba d’eissa kaman?
Rav Akiva Eiger, in his Gilyon HaShas on Chullin 12a, cites Rashi’s commentary to a later Gemara in Chullin. Rashi states there that the source for following a ruba d’lessa kaman is from one of two sources that the Gemara cited earlier that were not disproved. Seemingly Rav Akiva Eiger is asking about a contradiction in the source for the halacha instructing us to follow a ruba d’lessa kaman.