Question: What is Rav's source that Bechor is eaten for two days and a night?

Answer: "U'Vesaram Yihyeh Lach ka'Chazeh ha'Tenufah uch'Shok ha'Yamin" equates Bechor to Chazeh v'Shok (of Shelamim), which are eaten for two days and a night.

Bei Rav do not learn from here, for perhaps it is equated to Chazeh v'Shok of Todah, which is eaten for one day and a night.

Rav admits that the Hekesh teaches only one day and a night. The verse ends "Lecha Yihyeh" to add more time (the second day) to eat.

Bei Rav disagree. Perhaps "Lecha Yihyeh" teaches that a Bechor Ba'al Mum is given to a Kohen, for we never find like this in the Torah (Tosfos- that Kohanim receive a disqualified Korban; Rashi - we have no other source for this).

Rav holds that "u'Vesaram" (plural) already teaches both Tam and Ba'al Mum.

Bei Rav says we cannot learn from this. Perhaps it refers to Bechoros of all Yisraelim.

(Mishnah): If it developed a Mum within its year, he may keep it (alive) for 12 months. (After its year, he may keep it for only 30 days.)

Question: How do we understand this?

Perhaps it is all one clause. If the Mum came within its year, he may keep it for 12 months and 30 days (from its birth);

Or, perhaps it is two clauses. If the Mum came within its year, he may keep it until 12 months (Rashi - from its birth; Shitah - from when the Mum came). If the Mum came after its year, he may keep it for 30 days.

Version #1 (Rashi) Answer #1 (Beraisa): Nowadays (after the Churban), before one has the opportunity to show a Bechor to a Chacham (because it is still Tam), one may keep it for two or three years. (He need not lock it up to die);

Version #2 (Tosfos) Answer #1 (Beraisa): Nowadays, before one has the opportunity to show a Bechor to a Chacham (because a Chacham is not here), one may keep it for two or three years (he need not go to where there is a Chacham);

After one (Rashi - a Yisrael; Tosfos - a Kohen) has the opportunity to show it to a Chacham:

If the Mum came within its year, he may keep it until 12 months. After its year, he should be required to slaughter it immediately;

However, to avoid a loss (Rashi - perhaps the meat will spoil before a Kohen comes to take it; Tosfos - if the Kohen can make better use of the meat later), he may keep it for 30 days. (Rashi - we assume that this is all one clause. Rashash - we assume that it is not one clause, for a Heter to keep it for 12 months suffices to avoid loss!)

Rejection: Also the Beraisa can be understood either way!

Perhaps (it is two clauses. If the Mum came within its year, he may keep it until 12 months. If the Mum came) after its year, he may keep it for 30 days (to avoid a loss);

Or, (it is all one clause;) even if the Mum came within its year, he may keep it 30 extra days after 12 months.

Answer #2 (Beraisa): If a Mum came 15 days before the end of its year, he may keep it until 15 days after the year, to complete 30 days.

This shows that the Mishnah is two clauses. Thirty days are allowed for a Mum that comes after the year.

Version #1: This supports R. Elazar;

(R. Elazar): If a Mum comes after the year, 30 days are allowed (before slaughtering it).

Version #2 - Question (R. Elazar): What is the source that if a Mum came within its year, he may keep it for 30 days after the year?

Answer - Question: "Lifnei Hash-m Elokecha Sochalenu Shanah v'Shanah" - which part of a year is considered like a year?

Answer: Thirty days are like a year (to be considered a second year animal).

Question (Beraisa): If a Mum came 15 days before the end of its year, he may keep it until 15 days after the year, to complete 30 days.

We grant the completion of 30 days for a Mum that came within the year are allowed, but not 30 full days after the year.

R. Elazar is refuted.

(Mishnah - R. Yehudah): If one slaughtered a Bechor and afterwards showed the Mum to an expert, it is permitted;

R. Meir forbids, because it was not slaughtered according to an expert.

If an amateur permitted a Bechor (i.e. said that it has a Mum Kavu'a) and it was slaughtered according to his ruling, it must be buried, and the amateur must pay.

(Gemara - Rabah bar bar Chanah): All agree that if the Mum was Dakin (a film in the eye), it is forbidden, for it can change. (Perhaps it was not Kavu'a before Shechitah, the pain of death caused it to look Kavu'a);

They argue about Mumim elsewhere on the body. R. Meir decrees due to Dakin, and R. Yehudah does not decree.

Support (Beraisa): If one slaughtered a Bechor and afterwards shows the Mum to an expert:

R. Yehudah says, if the Mum was Dakin, it is forbidden, for it can change. If the Mum was elsewhere on the body, it is permitted, for it does not change;

R. Meir forbids in both cases, for it can change.

Objection: Surely, Mumim elsewhere do not change!

Correction: Rather, it is forbidden due to those Mumim that change.

Rav Nachman bar Yitzchak: Also our Mishnah supports Rabah!

(Mishnah - R. Meir): It is forbidden, because it was not slaughtered according to an expert.

This shows that R. Meir's law is a fine. (Ramban - really, it is just a decree, since it applies even if the owner is blameless, e.g. someone else slaughtered it.)

Question: R. Meir forbids due to those Mumim (e.g. Dakin) that change;

Do they always change, or only sometimes?

Question: What difference does it make? (In any case, the animal must be buried, for perhaps it changed)!

Answer: If witnesses testify that the Mum did not change appearance at all:

If Dakin always change, we reject their testimony. If sometimes they do not change, we accept it and permit the animal.

Answer (Rabah bar bar Chanah): R. Yoshiyah of Usha said to me "come, and I will show to you Dakin that change." This implies that not all Dakin change.

(Mishnah): If an amateur permitted a Bechor and it was slaughtered according to his ruling, it must be buried, and the amateur must pay.

Suggestion: Our Stam (anonymous) Mishnah is like R. Meir (who forbids no matter where the Mum was).

Rejection: Perhaps it discusses Dakin. It is according to everyone.

(Beraisa): If the amateur permitted a small animal, he pays a quarter of its value. For a large animal, he pays half (for perhaps it was not a Mum Kavu'a, and the animal would have died without getting a Mum, so the owner did not lose anything).

Question: What is the reason (why he pays less for a small animal)?

Answer #1 (Rav Papa): Small animals are worth less. It is a smaller loss.

Rejection: In each case he should pay the same proportion of the value!

Answer #2 (Rav Huna bar Mano'ach): One pays less because one may not raise small animals in (settled parts of) Eretz Yisrael. (The owner was relieved of a great burden of grazing the Bechor in unsettled places until an expert will permit it. Alternatively, if the Bechor was born to the Kohen's animal, he is punished for transgressing.)

(Mishnah): In the following cases, the verdict stands, and the judge pays for the loss he caused;

He acquitted the guilty or obligated the innocent, or was Metamei (declared to be Tamei) what is Tahor, or was Metaher what is Tamei.

A Mumcheh (expert) authorized by Beis Din is exempt.

(Gemara) Suggestion: Our Stam (Mishnah is like R. Meir, who obligates for Garmi (causing damage. Most Rishonim hold that this is more direct or more likely to cause damage than Gerama, for which all agree that one is exempt.)

Rejection (R. Ilai): It is according to everyone. The case is, the judge himself executed his mistaken ruling and transferred the money from one party to the other.

Question: We understand obligating the innocent. He took Reuven's money and gave it to Shimon;

What is the case of acquitting the guilty?

If he said "you are exempt," he did not transfer money!

Answer (Ravina): Reuven had a security from Shimon (for a debt). The judge exempted Shimon, took the security from Reuven and gave it to Shimon.

The case of being Metamei what is Tahor is when the judge touched a Sheretz to Reuven's food (so Reuven will not contest the ruling that it is Tamei);

The case of being Metaher what is Tamei is when he mixed it (what he mistakenly said is Tahor) with Reuven's (Tahor) food.

(Mishnah): A case occurred in which a cow's womb was removed. R. Tarfon ruled that the cow is Terefah. They fed it to dogs;

Chachamim in Yavneh were Machshir, because Mitzriyim cut the wombs of all cows and pigs that leave Mitzrayim (so they will not reproduce, yet they live).

R. Tarfon: I will lose my donkey to pay for my mistake! (Ein Eliyahu - I am considered a damager. I must pay even from property essential for one's livelihood.)

R. Akiva: You are Mumcheh l'Rabim, therefore you are exempt.

(Gemara) Question: Even if R. Tarfon was not a Mumcheh, he would be exempt, for he erred bi'Dvar Mishnah (a clear mistake);

If a judge erred bi'Dvar Mishnah, we retract the verdict!

Answer: Indeed, R. Akiva gave a second reason to exempt him:

Since you erred bi'Dvar Mishnah, we retract the verdict;

Even had you erred b'Shikul ha'Da'as (when two Tana'im (or Amora'im) argue with each other, and the Halachah was not established like either one, but the discussion favors one opinion, and a judge ruled like the other opinion), you would be exempt, since you are a Mumcheh l'Rabim.