Answer #2 (Abaye): It means, the same applies to joining for the Shi'ur of Tum'ah during Pesach;

During the rest of the year, there is a distinction.

Question: What is the case?

Answer: Less than k'Beitzah of food touched the dough:

During Pesach, the Isur of Chametz makes the dough significant, therefore it joins to comprise a Shi'ur;

During the rest of the year, it depends on whether or not he is Makpid - if he is Makpid about it, it is a Chatzitzah; if he wants it to stay there, it is like part of the trough.

Objection (Rava): The Mishnah does not discuss joining - it discusses a Chatzitzah!

Answer #3 (Rava): It means, the same applies to being Metaher the trough.

Question: What is the case?

Answer: It became Tamei, and he wants to immerse it to Metaher it:

During Pesach, the Isur makes the dough significant, therefore it is a Chatzitzah that invalidates immersion;

During the rest of the year, it depends on whether or not he is Makpid - if he is Makpid about it, it is a Chatzitzah; if he wants it to stay there, it is like part of the trough.

Objection (Rav Papa): The Mishnah does not discuss Taharah - it discusses Tum'ah!

Answer #4 (Rav Papa): It means, the same applies to being Metamei the trough.

Question: What is the case?

Answer: A Sheretz touched the dough:

During Pesach, the Isur makes the dough significant, therefore it is a Chatzitzah, and the trough is not Tamei;

During the rest of the year, it depends on whether or not he is Makpid - if he is Makpid about it, it is a Chatzitzah; if he wants it to stay there, it is like part of the trough.

(Mishnah): If one has 'Cheresh' dough (one cannot tell whether or not it is Chametz; alternatively, it is as hard as Cheres (earthenware)) - if other dough that was kneaded at the same time became Chametz, the Cheresh dough is also forbidden.

(Gemara) Question: If there is no other dough that was kneaded at the same time, what is the law?

Answer (R. Avahu): If from the end (R. Chananel, Rambam; Ritva - beginning) of kneading enough time has elapsed to walk from the tower of Nuyna to Tiverya, a Mil (2000 Amos, about a kilometer - this is 18 or 22 and a half minutes - see note in Appendix for 93B.)

Question: Why didn't he simply say 'the time to walk a Mil'?

Answer: In passing, he teaches how much is a Mil.

Version #1 (R. Avahu): One must walk [up to] four Mil for the following:

To knead a dough b'Taharah (Rashi - one hired to do so must walk four Mil to immerse vessels without extra compensation; Tosfos - if one wants to knead dough, he must walk four Mil to get someone who can do so b'Taharah);

To pray [with a Tzibur];

To wash his hands [before eating].

Version #2 (Rav Nachman bar Yitzchak): Eibo said this, not R. Avahu; he included a fourth case, tanning:

(Mishnah): [Soft hide is Mekabel Tum'as Ochlim -] if any non-human hide was tanned or trampled enough for tanning, it is Tahor.

Question: How long is enough for tanning?

Answer (R. Yanai): It is [the time to walk] four Mil.

(R. Yosi bar Chanina): Four Mil is the Shi'ur in the direction one was going, but one need not backtrack even one Mil.

Inference (Rav Acha): One must backtrack any amount less than one Mil.

(Mishnah) Question: How may Reuven separate Chalah from a Tamei dough on Yom Tov [of Pesach? If he designates part of the dough to be Chalah, he may not bake it [it is not a need of Yom Tov, since no one may eat Tamei Chalah], and it will become Chametz!]

Answer #1 (R. Eliezer): He does not specify which part is Chalah until it is baked.

Answer #2 (Ben Beseira): He [designates part of the dough to be Chalah, and] puts it into cold water to impede Chimutz.

Answer #3 (R. Yehoshua): He is not commanded Bal Yera'eh and Bal Yimatzei regarding this Chametz! He may leave it until Motza'ei Yom Tov - he is not concerned if it becomes Chametz.

(Gemara) Suggestion: The Tana'im argue about whether or not Tovas Hana'ah (Reuven's right to choose to which Kohen he will give Chalah [or tithes] - a Kohen's mother would pay a small amount to Reuven to give it to her son) is k'Mamon (like a monetary stake in the Chalah):

R. Eliezer holds that it is like money; R. Yehoshua holds that it is not like money [therefore, the Chalah is not Reuven's, so he is not commanded about it].

Rejection: No, all agree that it is not like money - they argue about Ho'il (does the law depend on something that could happen):

R. Eliezer says, Ho'il (since) one may annul his declaration of Chalah, and it reverts to be his, therefore it is considered his [even if he does not annul it. Ho'il would also allow baking Tamei dough that was already made Chalah - however, it is better to avoid relying on Ho'il.]

R. Yehoshua does not say Ho'il.

(Rav Chisda): If one bakes on Yom Tov for the sake of a weekday, he is lashed;

(Rabah): He is not lashed.

Rav Chisda obligates lashes - we do not exempt Ho'il (since) if guests would come he could serve the food to them [and it turns out that he cooked for consumption on Yom Tov];

Rabah exempts - we say Ho'il.

Question (Rabah against Rav Chisda): You do not say Ho'il - how may we cook on Yom Tov for Shabbos (when Yom Tov is on Erev Shabbos?)

Answer (Rav Chisda): It is permitted through Eruv Tavshilim (one begins preparing for Shabbos before Yom Tov, and may prepare more on Yom Tov).

Question (Rabah): Eruv Tavshilim [is mid'Rabanan, it] cannot permit an Isur mid'Oraisa!

Answer (Rav Chisda): Mid'Oraisa, one may cook on Yom Tov for Shabbos - Chachamim decreed, lest people come to cook on Yom Tov for the sake of a weekday;

Chachamim required Eruv Tavshilim to remind people that one may not cook freely on Yom Tov for the sake of other days.

Question (Rabah - Beraisa): If an animal is about to die [on Yom Tov], one may slaughter it only if there is enough time to eat a k'Zayis roasted (this is the fastest way to cook) before night;

It suffices that he could eat, even if he does not eat.

According to me, Ho'il he could eat, he may slaughter;

But you do not say Ho'il - if he will not eat, why may he slaughter?

Answer (Rav Chisda): It is permitted lest he lose money [the animal will die without slaughter].

Objection (Rabah): We do not permit an Isur mid'Oraisa to prevent a loss of money!

Answer (Rav Chisda): To avoid losing money, he resolves to eat a k'Zayis before dark - this necessitates slaughtering.