1) "UNTIL THE GROUND"
OPINIONS: Rebbi Yirmeyah (end of 123b) challenges the view of Reish Lakish from the Mishnah in Kelim (5:7). The Mishnah says that in order to be Metaher an oven that became Tamei, one must break it into three parts and scrape off the plaster "until the ground." What does the Mishnah mean when it says "until the ground"?
(a) The RASH in Kelim and RASHI here (DH Ad) explain that the Mishnah means that the plaster around the oven must be removed until ground level.
(b) The Rash there suggests further that when one breaks the oven into three pieces, the cracks must reach all the way down to the ground. It is not sufficient to crack the oven partially.
(c) The RAMBAM (Perush ha'Mishnayos to Kelim) explains that the plaster underneath the oven must be removed until the oven itself rests on the ground and is no longer attached to the ground with plaster.
The VILNA GA'ON in Kelim adds that the Rambam's explanation best fits the wording of the Mishnah, because the Mishnah says, "Ad she'Yehei ba'Aretz," using the masculine form of "it will be" -- "she'Yehei." The word "Tanur" (oven) is masculine, while "Tefeilah" (plaster) is feminine.
QUESTION: The Mishnah discusses the hide of an animal that has a k'Zayis of meat (of Neveilah) attached to it. The Mishnah says that one who touches a "Tziv" that protrudes from the meat, or a hair that is opposite the meat, becomes Tamei. RASHI (DH Tziv) explains that a Tziv is a strand of flesh protruding from the meat and which is loosely attached to the meat. The Tziv itself does not contain a k'Zayis of meat, but it makes the person who touches it become Tamei because it is attached to the piece of meat that is a k'Zayis.
Rashi's explanation of the Mishnah is difficult to understand. If the point of the Mishnah is to teach that the Tziv causes a person who touches it to become Tamei even though it is only loosely attached to the original piece of meat, then why does the Mishnah need to discuss a case of a hide that has a k'Zayis of meat on it? It would suffice for the Mishnah to say merely that one who touches a Tziv that protrudes from a k'Zayis of Tamei meat becomes Tamei! Why does the Mishnah need to mention the hide at all?
Moreover, why does the Mishnah need to teach that the Tziv conveys Tum'ah? In every case in which a person touches Tum'ah, the person needs only to touch part of the Tum'ah and not the entire quantity of the Tamei item. Why is touching a Tziv different from touching any other part of the meat? (TIFERES YAKOV)
(a) The TIFERES YAKOV answers that there certainly is no novelty in saying that a strip protruding from Tamei meat also causes one to become Tamei. What, then, is the Chidush of the Mishnah? We know that the hide is Mevatel any attached meat that is less than a k'Zayis, as the Gemara says later. Rebbi Akiva (124b) even maintains that when there are two pieces of meat attached to the hide that, when combined, equal a k'Zayis of meat, the hide is still Mevatel the meat. The Mishnah therefore teaches that although small pieces of meat are nullified by the hide, when a small piece of meat (a Tziv) is attached to a piece of meat that is a k'Zayis, it retains its identity and is not nullified. This also explains why the Mishnah discusses meat attached to a hide; the whole point of the Mishnah is to teach that in this case the hide does not annul the small piece of meat.
(b) The Tiferes Yakov suggests another explanation. The hide, in the Mishnah's case, might be supporting the meat as well as the Tziv. If the skin would be peeled away, the Tziv also would become separated from the k'Zayis piece of meat. One might have thought that since the Tziv's entire connection to the meat is due only to the skin, it is not considered connected to the meat, and thus one who touches it does not become Tamei. The Mishnah, therefore, teaches that it is still considered part of the meat.
(c) The Tiferes Yakov points out that he gives these two explanations only in order to explain the Mishnah according to Rashi's interpretation of "Tziv." If not for Rashi's interpretation, he would have suggested that the Tziv is actually strips of the skin which are on the same side as the meat. He says that this is apparently the interpretation of the RAMBAM (in Perush ha'Mishnayos). Accordingly, the Mishnah is teaching the novel law that touching a strip of skin located near the meat makes one Tamei as though he touched the meat itself. The Tiferes Yakov favors this explanation. (Y. MONTROSE)
3) "EVEN IF YEHOSHUA BIN NUN WOULD HAVE TOLD ME THIS"
QUESTION: The Gemara relates that there were times at which Rebbi Oshiya found Rebbi Ami teaching the statement of Ula in the name of Rebbi Yochanan with regard to the end of the Mishnah. When Rebbi Oshiya asked Rebbi Ami that the statement of Ula in the name of Rebbi Yochanan was said with regard to the first part of the Mishnah, Rebbi Ami replied, "ha'Elokim! Even if Yehoshua bin Nun would have told me this, I would not have paid attention to him!"
If Rebbi Ami wanted to emphasize that he did not accept that Rebbi Yochanan's statement was said with regard to the first part of the Mishnah, why did he mention only Yehoshua bin Nun? He should have said, "Even if Moshe Rabeinu would have told me this..."!
ANSWER: The SHULCHAN ARUCH (YD 242:36) rules that a person is punished with Malkus (d'Rabanan) for saying to his friend, "Even if you would be Moshe Rabeinu, I would not agree with you!" Such talk is considered a disgrace to Moshe Rabeinu.
The VILNA GA'ON (BI'UR HA'GRA YD 242:82) explains that the source for the Shulchan Aruch's ruling is the Gemara here, in which the Amora'im mention only Yehoshua and not Moshe Rabeinu.
The TAZ (YD 242:20) explains that the source in the Torah that it is disrespectful to Moshe Rabeinu to say to someone, "Even if you would be Moshe Rabeinu...," is the verse, "No prophet ever arose in Yisrael like Moshe" (Devarim 34:10).
4) COMBINING TWO HALF "K'ZEISIM" TO CAUSE "TUM'AH"
QUESTION: Rebbi Yochanan says that Rebbi Yishmael and Rebbi Dosa are of the same opinion with regard to combining partial Shi'urim of objects to cause Tum'ah. The Gemara quotes the Mishnah in Ohalos (3:4) in which Rebbi Dosa says that two half-k'Zeisim of a Mes that enter a house do not combine to make the house Tamei with Tum'as Ohel.
How can Rebbi Yochanan say that Rebbi Yishmael agrees with Rebbi Dosa? Rebbi Yishmael rules that two such pieces do combine to make one who carries them Tamei with Tum'as Masa, since they both are being carried at once. Accordingly, Rebbi Yishmael also should maintain that two half-k'Zeisim that are under the same roof combine to be Metamei with Tum'as Ohel.
(a) The RASHBA (DH Ha), quoting the RA'AVAD, explains that carrying two half-k'Zeisim of a Mes can be done in a single act of carrying. However, when two pieces of Mes are under one ceiling, a different part of the ceiling is covering each one, and it is as though they are under two different ceilings. RASHI (DH Metaher) mentions a similar line of reasoning.
(b) TOSFOS (DH Ein) explains that with regard to carrying parts of a Mes, the Gemara derives from a verse (Vayikra 11:25; note that the verse is not quoted accurately by the Gemara or Tosfos) that two half-k'Zeisim can be combined to create Tum'ah. Since the verse does not mention Tum'as Ohel, we cannot derive from the verse that two half-k'Zeisim combine with regard to Tum'as Ohel.