QUESTIONS ABOUT MEASUREMENTS
(R. Papa): Do we calculate the Koseves with or without its seed?
(R. Ashi): Do we calculate a Se'orah (an "Etzem" for Tum'as Meis) with or without its shell?
Also, are we speaking of a moist or dry Se'orah?
R. Ashi relies on 'ha'Gasah' to address the question of R. Papa.
R. Papa relies on the word 'Se'orah' as opposed to Oshlah (which is a Se'orah without its shell) and as opposed to Shiboles (which is moist Se'orah) to address R. Ashi's questions.
THE KOSEVES IS LARGER THAN A KEBEITZAH
(Rabah citing R. Yehudah): The Koseves ha'Gasah (of our Mishnah) is larger than a Beitzah.
Chazal understood that a Koseves is the minimum amount required for one to feel satisfied.
The violation of Yom Kipur occurs when one loses the Inuy of not eating, not when one actually eats (which would be a k'Zayis).
Question: From the incident in the Mishnah in Sukah we see that two Kosavos are less than a k'Beitzah, such that it seems unlikely that one, even plump, Koseves with its pit could be larger than a k'Beitzah!?
Food was brought on Sukos to R. Yochanan b. Zakai and two Kosavos and a pitcher of water were brought to R. Gamliel.
In both instances, the Tana instructed them to bring the food to the Sukah.
The Beraisa reports that this was not required, but was their Chumrah.
When R. Tzadok was given less than a k'Beitzah of bread he allowed three leniencies (including eating it outside the Sukah) but if it was a k'Beitzah, it would require a Sukah.
Thus it seems that the two Kosavos brought to R. Gamliel were smaller than a k'Beitzah!
Answer (R. Yirmiyah): Indeed, two Kosavos without their pits are less than a k'Beitzah, while one plump Koseves with its pit is larger (the volume of the pit is greater than the meat, as R. Papa reported the common knowledge that the pits comprise a bit more than 50% of the bushel).
Answer (Rava): Actually two Kosavos are larger than a k'Beitzah, but fruit never requires Sukah, and that is why they need not have brought it into the Sukah.
Question: But we learned in the Beraisa that any Achilas K'va requires Sukah!?
Rebbi reported that when learning under R. Elazar b. Shamua they were brought figs and grapes and they ate them Achilas Arai outside of the Sukah.
We may infer from this that Achilas K'va (even of the fruit) would have necessitated the Sukah!
Answer: Rebbi meant that they ate even a large amount in an Arai fashion outside of the Sukah.
Alternate Answer: There was a large quantity of fruit and they ate bread outside of the Sukah Achilas Arai, as well.
The Beraisa seems to support Rava's assertion:
The 14 meals of Sukos may be filled in with Targima (dessert).
If fruit could fill in, then the Beraisa should have mentioned fruit (thus indicating that fruit does not require Sukah).
No, the word 'Targima' could also mean fruit dessert!
Alternately, the Beraisa was speaking in a place where fruits were not common, and thus used a dessert which does not imply fruit, with no intention to exclude fruit.
THE KOSEVES IS SMALLER THAN A KEBEITZAH
(R. Zvid): The Koseves ha'Gasah of our Mishnah is smaller than a k'Beitzah.
This is supported by the manner in which the position of Beis Shamai is taught in the Mishnah in Beitzah:
Beis Shamai say that the Shiur Chiyuv of Se'or is a k'Zayis and of Chametz is a ke'Koseves.
Their source for differentiating is the fact that the Torah writes the Isur by "Se'or", as well, even though it could logically be derived from Chametz (since Se'or is a more potent form of Chametz) as similarly being a k'Zayis.
Now if a ke'Koseves was larger than a k'Beitzah, then Beis Shamai, when looking for a larger Shiur for k'Zayis, would have first come upon k'Beitzah.
Even if they (Koseves and Beitzah) were the same size, k'Beitzah is far more familiar and would have been used!
We may thus infer that a ke'Koseves is smaller than a k'Beitzah.
Question: Perhaps a standard Koseves is indeed smaller than a Beitzah, but a Koseves ha'Gasah is larger!?
Answer (still R. Z'vid): Rather, my proof is from the Mishnah in Berachos where a k'Beitzah is listed as satisfying.
For Zimun the participants need to have eaten a k'Zayis according to R. Meir and a k'Beitzah according to R. Yehudah.
R. Yehudah holds that the Pasuk teaches that for Birkas ha'Mazon the food must fulfil "ve'Sava'ta", which is a k'Beitzah.
If a k'Beitzah is satisfying, surely it is enough to remove the sense of Inuy required for the prohibition on Yom Kipur!?
Thus we see that a Koseves ha'Gasah must be smaller than a k'Beitzah.
To summarize, k'Beitzah satisfies (for the purposes of Birkas ha'Mazon) while a ke'Koseves settles the mind of the eater, invoking the prohibition on Yom Kipur.