Objection: Our case is unlike Ula's case!

Granted, it is similar if Reuven married Rachel, then his brother Shimon married her sister Leah, and Reuven died. Since Eshes Ach is permitted, also Achos Ishto would be permitted (if not for "Aleha").

Question #1: If Shimon married before Reuven, the Isur of Achos Ishto came first (and it is not permitted)!

Question #2: Even when Reuven married before Shimon, the comparison is good only if Reuven died before Shimon married. In this case, Rachel was permitted in the interim.

However, if Reuven died after Shimon married Leah, Rachel was never permitted!

Surely Ula agree that that if a Metzora had an emission on the night of his eighth day he may not enter his thumb into the Mikdash, since there was never a time when he could bring his Korban (and enter it)!

Answer: Indeed, "Aleha" is needed only for the case when Reuven married and died before Shimon married.

Answer #4 (to Question 5:b): If not for "Aleha", we would learn from a Hekesh that all Arayos may do Yibum.

(R. Yonah): "All... will get Kares" - all Arayos are equated to Eshes Ach.

One might have thought that just like Eshes Ach is permitted (for Yibum), all Arayos are permitted. "Aleha" teaches that this is not so.

Question (Rav Acha mi'Difti): The other Arayos can be equated to Eshes Ach, or to Achos Ishto. Why do we equate them (above, Daf 3b) to Achos Ishto and not to Eshes Ach?

Answer #1 (Ravina): We equate to be stringent, not to be lenient.

Answer #2 (Ravina): Each of the other Arayos has two Isurim (itself, and Eshes Ach). It is better to learn from Achos Ishto, which also has two Isurim, and not from Eshes Ach, which has only one.

Answer #5 (to Question 5:b - Rava): We do not need a verse to forbid the Ervah, for an Aseh does not override a Lav with Kares;

Aleha is needed to forbid the Tzarah.

Question: We need a verse to teach that the Ervah is forbidden!

(Beraisa): 'This only teaches me about her (the Ervah)... '

Answer: This was said only to show the source of the Isur of the Tzarah.

Question (Beraisa): 'This only teaches about them (the Arayos)... '

Answer: This was said only to show the source of the Isur of their Tzaros.

Question (Beraisa - Rebbi): "He will take her and do Yibum (to) her" - these (exclude, and thereby) forbid Tzaros and Arayos.

Answer: It should say 'the Tzaros of Arayos.'

Question: Two words were expounded (surely, we learn two laws)!

Suggestion: One teaches about the Ervah, and one about the Tzarah!

Answer: No, both teach about the Tzarah. One forbids her in the situation of Yibum, and one permits her not in the situation of Yibum.

Question: How do we know this?

Answer: "He will do Yibum (to) her" - the Isur (of the Tzarah) is only in the situation of Yibum.

(Rav Ashi): The Mishnah supports Rava.

It teaches that 15 Arayos exempt their Tzaros. It does not need to say that the Arayos themselves are exempt!

Question: Surely, Ervah does not require a verse because an Aseh does not override a Lav with Kares. Similarly, we do not need "Aleha" to forbid the Tzarah ("Litzror" forbids her like Ervah, and there is Kares for all Arayos).

Answer: (Rav Acha bar Bivi): Indeed, Rava does not use "Aleha" to forbid the Tzarah, rather, to permit her when there was no fall to Yibum!

Question: How do we learn this?

Answer #1: It says "(Litzror) Aleha" - she is prohibited only in the situation of "(Yevamah Yavo) Aleha".

Question (Rami bar Chama): Perhaps the Ervah herself is permitted not in the situation of Yibum!

Answer (Rava): A Kal va'Chomer refutes this. Ervah is forbidden even in the situation of Yibum, all the more so when there is no Mitzvah!

Question (Rami bar Chama): The Tzarah disproves this. She is forbidden in the situation of Yibum, and otherwise permitted!

Answer (Rava): The Torah wrote "In her lifetime" to disprove this reasoning. She (Achos Ishto, the wife's sister) is forbidden in her (the wife's) entire lifetime.

Question: We need this verse to permit Achos Ishto after the wife dies!

Answer: That is learned from "Ishah El Achosah" (she is forbidden only when they are together;

Objection: Had it written only this, one might have thought that she is permitted after the wife is divorced. Therefore, also "In her lifetime" is needed!

Answer #2 (Rav Huna bar Tachlifa) - Question: It says "Ishah El Achosah Lo Sikach Litzror" (both are forbidden). The verse concludes "Legalos Ervasah (singular)."

Answer: Both are forbidden in a situation of Yibum. Elsewhere, the Ervah is forbidden and the Tzarah is permitted.

Question: Perhaps in a situation of Yibum, the Ervah is forbidden and the Tzarah is permitted, and elsewhere, they are both forbidden!

Answer: If so, the Torah would have omitted "Aleha".

Question (Rav Ashi): How do we know that "Aleha" forbids? Perhaps it permits!

"Ishah El Achosah Lo Sikach" forbids both, not in the situation of Yibum. Regarding Yibum, both are permitted!

Answer: If so, we could not fulfill "Legalos Ervasah (singular)";

In the situation of Yibum, both are permitted. Not in the situation of Yibum, both are forbidden!

(Beraisa - Rebbi): "He will take her and do Yibum (to) her" - these (exclude, and thereby) forbid Tzaros and Arayos.

Question #1: The verse does not discuss Tzaros and Arayos!

Question #2: We derive Tzaros from Litzror!

Answer (to Question #2): Rebbi uses Litzror for R. Shimon's teaching (28b, that two sisters who fall to Yibum (from different brothers) are exempt).

Answer (to Question #1): It says "He will take her" to teach that when there are two women to be taken (Yevamos), and the Yavam can take whichever he wants, they are permitted. If not, both are forbidden.

"He will do Yibum (to) her" - in the situation of Yibum, the Tzarah is forbidden. Elsewhere, she is permitted.

Question: What do Chachamim learn from "He will take her"?

Answer: This teaches R. Yosi bar Chanina's law, that (after Yibum) the Yavam can divorce her with a Get (document) and (if he wants) remarry her;

"He will do Yibum (to) her" teaches that he may do so against her will.

Rebbi learns R. Yosi bar Chanina's law from "For a wife". He learns that Yibum works against her will from "Yevamah Yavo Aleha". (Malbim - elsewhere the Torah discusses Bi'ah El Ishah, denoting equality. Here it says Aleha, to show that he is dominant.)

Question: What does Rebbi learn from Aleha?

Answer (Beraisa): Beis Din brings Par Helam Davar (a Korban for a mistaken ruling which caused most of Yisrael to transgress) only if they permitted something punishable by Kares if done b'Mezid, and Chatas if (an individual did it b'Shogeg);

Likewise, a Kohen (Gadol) Mashi'ach (anointed with Shemen ha'Mishchah) brings a Par only for a transgression due to such a mistake.

Also, they bring for a mistaken ruling about idolatry only for something punishable by Kares b'Mezid and Chatas b'Shogeg.