1) THE LENGTH OF A "MIL" AND THE TIME IT TAKES FOR DOUGH TO BECOME CHAMETZ
QUESTION: The Gemara discusses the amount of time that it takes for dough to become Chametz. Reish Lakish says that dough becomes Chametz in the time that it takes a person to walk "from Migdal Nunya to Teverya, which is one Mil." The Gemara asks that Reish Lakish should say simply "the time that it takes to walk one Mil." Why does he add "from Migdal Nunya to Teverya"? The Gemara answers that Reish Lakish adds these words in order to teach, incidentally, the length of a Mil.
There is a similar discussion in the beginning of Megilah (2b). The Gemara there says that any settlement that is near a walled city has the status of the walled city and reads the Megilah on the fifteenth of Adar. The Gemara asks how close must such a settlement be to the walled city in order to attain the status of that walled city. Rebbi Yirmeyah (or, according to some, Rebbi Chiya bar Aba) answers that it must be no more than the distance "from Chamsan to Teverya, which is one Mil." The Gemara there asks, as it does here, that he should say simply "one Mil," and it answers that he adds the words "from Chamsan to Teverya" in order to teach the length of a Mil.
Why does the Gemara here and in Megilah interpolate a lesson about the length of a Mil, which has nothing to do with the subject at hand?
Moreover, the length of a Mil is known already -- it is 2000 Amos. Why does the Gemara need to teach a practical example of the length of a Mil?
Finally, why does the Gemara give two different measurements for the length of a Mil, "from Migdal Nunya to Teverya," and "from Chamsan to Teverya"? (TUREI EVEN to Megilah 2b, cited by the GILYON HA'SHAS here)
(a) The TUREI EVEN answers that there are two ways to measure a Mil. Although the actual length of a Mil is 2000 Amos, the Gemara in the beginning of Eruvin (3b) teaches that there are two different types of Tefach, and thus two different types of Amah, with different lengths. An Amah can be an exact Amah, or it can be a slightly elongated one ("Sochakos"). Accordingly, there are two types of Mil as well, a long one and a short one.
This is the basis for understanding the Gemara here. With regard to Chametz, this Halachah is stringent, and dough that was left for the amount of time that it takes a person to walk the shorter Mil is considered Chametz. In order to demonstrate this point, Reish Lakish adds that a Mil in this context is calculated as "the time that it takes to walk from Migdal Nunya to Teverya" -- the distance of which is one short Mil.
In contrast, the Halachah with regard to the reading of the Megilah involves no stringency; the only question is on which day a town near a walled city should read the Megilah, on the fourteenth or the fifteenth of Adar. Therefore, the measure used to determine whether the town is considered part of the walled city is one long Mil. The Gemara in Megilah emphasizes this by giving an example of a long Mil -- the distance from Chamsan to Teverya.
(b) While most other Halachic Shi'urim are Halachos l'Moshe mi'Sinai (such as the minimum size of a Sukah, and the minimum distance that one must separate two types of crops from each other), the Shi'ur of one Mil -- the amount of time that it takes dough to become Chametz -- is certainly not a Halachah l'Moshe mi'Sinai. Rather, the Mil here is utilized merely as a measure of time, and that time span is determined by the practical consideration of the time that it takes dough to become Chametz. In fact, the Halachah is that if dough does not develop cracks in that amount of time, the dough indeed is not Chametz, as the Mishnah here says. Consequently, there is no reason to think that the time that it takes for dough to become Chametz is unconditionally linked to the exact amount of time that it takes a person to walk one Mil. (For this reason, it is also inappropriate to treat this time span stringently, as though it were a Shi'ur of an Isur d'Oraisa for which we should be Machmir, as the Turei Even suggests.) This Shi'ur is different from other Shi'urim, such as the dimensions of a Sukah, the distance between grapevines and wheat plants with regard to Kil'ayim, the amount of Matzah one must eat to fulfill the obligation, and so on, which are established either by the Torah (Halachah l'Moshe mi'Sinai), or by the Rabanan according to what they discern is considered a significant quantity, size, or distance for each particular item in question.
For this reason, the Gemara does not say simply that the time that it takes for dough to become Chametz is one Mil, but it adds "the time it takes to walk from Migdal Nunya to Teverya." Dough becomes Chametz in approximately the amount of time that it takes to walk one Mil, but not exactly that amount of time (but slightly more). Therefore, the Gemara adds a more exact measure; the amount of time that it takes to walk from Migdal Nunya to Teverya.
Similarly, the Gemara in Megilah is discussing a Halachah mid'Rabanan (the reading of the Megilah). The date on which a town reads the Megilah depends on the practical question of which suburbs of a walled city are subordinate to that city, due to the fact that the residents are often found in the walled city. The Mil-measurement there may not refer to the normal Mil, but rather it refers to an approximate Mil; the exact distance must be determined by a number of circumstances (for example, is the approach to the walled city easy or difficult). Therefore, the Gemara gives a practical example of the distance by defining it as the distance from Chamsan to Teverya.
When the Gemara in both places concludes that "he means to teach that the distance of a Mil equals the distance between these two places," it means that the Amora's intention is to teach that in ordinary, everyday usage ("Lashon Bnei Adam"), even such distances may be referred to as "one Mil" (with practical ramifications for business deals in which a Mil is mentioned).
Perhaps an additional explanation may be suggested for why the Gemara chose these specific examples of the length of a Mil. The Gemara in Megilah (5b) concludes that in Teverya the Megilah is read on the fifteenth of Adar, as in walled cities. (It is also read on the fourteenth of Adar out of doubt.) According to the Gemara there, the Gemara earlier in Megilah is giving an example of the length of a Mil which has practical ramifications. Instead of saying merely that a town must be within one Mil of a walled city in order to be considered part of that city, the Gemara teaches that Chamsan is close enough to Teverya to have the specific Halachos of Teverya. Just as Teverya must read the Megilah on both the fourteenth and the fifteenth of Adar, so, too, Chamsan must read it on both days.
Similarly, in the case of the Gemara here, perhaps Migdal Nunya was a place where there was a building ("Migdal") with a flour mill. The Gemara teaches that if one kneads the dough there and brings it to Teverya in order to bake it, the dough will become Chametz by the time he reaches Teverya. That is why the Gemara gives specifically this example of the length of a Mil. (M. KORNFELD)

46b----------------------------------------46b

2) BAKING "TAMEI" DOUGH ON THE YOM TOV OF PESACH
QUESTION: The Mishnah discusses what to do with dough from which Chalah has not been separated, which one bakes on Yom Tov of Pesach, and which is Tamei (and thus cannot be given to a Kohen to eat).
He may not bake the entire batch of dough into Matzah first, and then, after it has been baked, separate Chalah from it, because one may not bake on Yom Tov for any purpose other than human consumption ("Tzorech Ochel Nefesh"), and the Chalah portion may not be eaten and thus is not baked for consumption. On the other hand, if he merely separates Chalah from the dough but does not bake the dough, he will not be able to dispose of the Tamei Chalah in the appropriate manner by burning it, because one may not burn Kodshim which are Tamei on Yom Tov. He also may not let it sit and wait until after Yom Tov to burn it, because if it sits it will become Chametz, and he will transgress the prohibition against having Chametz in his possession on Pesach. What, then, should he do with the dough?
Rebbi Eliezer says that he may bake the dough before he separates Chalah from it. Once it has been baked into Matzah (and there is no longer any concern that it will become Chametz), he may designate one of the loaves as Chalah. Why, though, is he permitted to bake something on Yom Tov which is not fit to be eaten? Rebbi Eliezer maintains that every loaf is fit to be eaten, because one can fulfill his obligation to separate Chalah by removing a small amount of Chalah from each individual loaf. Therefore, he may bake all of the dough, even though he ultimately decides to make one entire loaf Chalah. (This is called the principle of "Ho'il," "since": "since he could have done it in another, entirely permissible way, he is permitted to do it in this way as well.")
This is Rebbi Eliezer's reasoning as explained by RASHI (DH Ad she'Te'afeh) on the Mishnah, based on the Gemara later (48a). However, Rashi on the Gemara (46b, DH Lo d'Chulei Alma) seems to give a different explanation for Rebbi Eliezer's opinion.
Rashi says that according to Rebbi Eliezer, one may bake all of the dough in the oven and then make some of it Chalah, because any given loaf is not necessarily the one that is going to be Chalah (and thus, when each loaf is viewed individually, they are all fit to be eaten). Why does Rashi here not give the same reason that he gives in the Mishnah, where he says that all of the dough is considered fit to be eaten, since ("Ho'il") he could separate a little bit from each loaf?
ANSWER: The second explanation that Rashi gives for Rebbi Eliezer's opinion is mentioned in the Gemara later (48a). The Gemara there uses this logic to explain why Rebbi Eliezer permits one to bake all of the dough even without relying on the principle of "Ho'il." The Gemara explains that when each of the loaves is viewed individually, it is possible that this loaf is not the one that will be used for Chalah. Therefore, one should be permitted to bake all of them on Yom Tov without relying on the principle of "Ho'il." The principle of "Ho'il" is necessary only in order to permit one to bake the dough on the grounds that he could remove a little bit of Chalah from each loaf. Since he ultimately does not actually take Chalah from each loaf, but he separates one large loaf as Chalah, "Ho'il" must be applied to permit him to bake. If, however, he may rely on the logic that he is able to take a different loaf as Chalah and not this particular one, the principle of "Ho'il" is not necessary.
Accordingly, Rashi on the Mishnah writes that Rebbi Eliezer's reasoning is that one could take a little bit of Chalah from each loaf, because that reasoning is based on the principle of "Ho'il" which is the Gemara's initial assumption (48a) in understanding Rebbi Eliezer. (Rashi's explanation on the Mishnah always addresses the Mishnah based on the initial assumption of the Gemara.)
In the Gemara (46b), however, Rashi has a question on the opinion of Rebbi Eliezer. If, as the Gemara initially assumes, Rebbi Eliezer maintains that the principle of "Ho'il" permits one to bake all of the dough, then why does he require one to bake the dough first and then separate Chalah from it? Even if one separates Chalah before he bakes it, he still should be permitted to bake it all because of "Ho'il" -- since he could revoke the status of Chalah from the dough (through the process of "She'eilah") and then bake it, he should be permitted to bake it now without revoking its Chalah status!
Rashi understands that this is not a strong question if Rebbi Eliezer permits one to bake the dough because of "Ho'il," as will be explained below. However, according to the Gemara's conclusion that Rebbi Eliezer does not need to rely on "Ho'il" to permit one to bake the dough, this is a strong question. In order to address this question, Rashi switches to the explanation offered in the Gemara's conclusion, that one may bake all the loaves since each one might not be the one separated as Chalah.
According to the logic that one may bake the dough because of "Ho'il" ("since he could take off a little bit of Chalah from each loaf..."), if one separates Chalah from the dough before he bakes it, two "Ho'il"'s must be utilized. The first "Ho'il" is that he could revoke its Chalah status and bake the dough. However, once he revokes its Chalah status and bakes all of the dough, there is still a problem that one of the loaves is going to be made into Chalah and is not fit to eat. Therefore, another "Ho'il" must be utilized to permit the baking: since he could take off a bit of Chalah from each loaf, all of the loaves are considered fit to be eaten.
"Ho'il," however, does not apply to such an extent, and therefore this double "Ho'il" does not permit the baking. (TOSFOS (DH Ho'il #1) explains in the name of RASHBA (Rabeinu Shimshon mi'Shantz) that we do not apply a "double Ho'il." See the Gemara earlier, 38a.)
Since two "Ho'il"'s do not apply to permit an act, Rashi does not ask his question on the Gemara's initial assumption (48a) that Rebbi Eliezer's reason is "'Ho'il' that one could take a little Chalah from each loaf...." Rather, Rashi asks his question on the other way of understanding Rebbi Eliezer, that each individual loaf by itself might be the one that will be eaten. Rashi asks that Rebbi Eliezer should permit one to bake the dough even after he separates Chalah from it, because he could be "Sho'el" on the Chalah and then bake it, and then separate Chalah from one of the loaves later. This act utilizes a single "Ho'il." Even though one loaf eventually will be separated as Chalah, each one is considered fit for eating because each loaf by itself might not be Chalah.
This is why Rashi gives a different reason for why Rebbi Eliezer would permit one to bake all of the dough first and then separate Chalah. Rashi explains this way in order to be able to ask why Rebbi Eliezer does not say that one may separate Chalah first and then bake it, an act which would utilize only one "Ho'il" and not two! (-Based on MAHARSHA to Tosfos DH Ho'il.)