Question: What is the source that Ula agrees about this?

Also in Zevachim (32b), Ula answered one who challenged him from this Beraisa "mi'Tun'ach (this will be explained)"! Since a Metzora is permitted for his Tzara'as...

Inference: Mi'Tun'ach, i.e. from the load (Beraisa) you bring to burden (refute) me, I will bring a proof from there!

Summation of question: What proof can he (Ula) bring from the Beraisa?

Answer (R. Yitzchak): Ula infers from the words "he saw Keri that day". This implies that he saw during the day, but not at (i.e. the previous) night;

Inference: Because he was permitted for his Tzara'as, he is permitted also for his Keri. Therefore, it is clear to him that here Ula agrees if he saw Keri on the eighth night.

Question: According to Rav Asi, why does an Ailonis exempt her Tzarah? It is one Isur! (She is Eshes Ach without a Mitzvah of Yibum.)

Answer: No matter how you say, she is forbidden. We learn from "Asher Teled" to exclude an Ailonis. Therefore, also her Tzarah is forbidden. (Litzror equates her Tzarah to her);

The same applies to Eshes Achiv she'Lo Hayah b'Olamo.

Question: What is the reason for the one who argues with Rav Asi?

Answer: Since an Ailonis cannot do Yibum in any case, her Tzarah is considered like Tzaras Ervah not in the situation of the Mitzvah.

Suggestion: An Ailonis should be like Chayavei Aseh. We learn below (20a) that they do Chalitzah!

Rejection: The Torah explicitly excluded Ailonis. The Heter of Eshes Achiv does not apply to her.

Question: We need the verse at least for the case when the brother who [later] died married Leah, and he died, and then his brother married [Leah's sister], lest I say that since [Leah] was permitted, [regarding Eshes Ach, she] is permitted [even now that she is also Achos Ishah]!

Answer #1: Rava hold unlike Ula, and [rather,] he holds that Bi'ah b'Miktzas is not Bia'h. (He has no source to say "since it was permitted, it is [totally] permitted.")

Answer #2: We distinguish. Regarding a Ba'al Keri, all Tum'ah is one Shem (Isur), so we say "since he was permitted, he is totally permitted." One Lav forbids a Ba'al Keri and a Metzora;

However, here there are two Shemos, so we do not say "since she was permitted, she is totally permitted."

Question: Why doesn't [Ervah] need a verse? Doesn't Rava agree to R. Yonah's Hekesh [of all the Arayos to each other? They should all be permitted, just like Eshes Ach!]

Answer: He holds that they are equated regarding Isur, for the verse discusses this, but not regarding Heter.

Question: How could he err to say that we require [Aleha] to forbid the Tzarah more than the Ervah, since we learn Tzarah from Litzror, and there is Kares for the Tzarah just like for the Ervah?

Answer (R. Yitzchak): Also now, he wants to say that [Aleha] forbids the Tzarah, and [the only reason we need this is] to infer that not b'Mekom Mitzvah she is permitted, like Rav Acha concludes at the end.

Implied question: [We answer for Rava] "I would only know her (Ervah)" really teaches about her Tzarah!

Answer: This is not because we need a verse to forbid the Tzarah. Rather, it is to infer Heter Lo b'Mekom Mitzvah.

Implied question: We ask "why is Ervah different, that no verse is needed for it?..." (I.e. but we need a verse for the Tzarah!)

Answer: The Gemara erred about Rava's words. He did not explicitly explain that "Aleha" comes to permit Lo b'Mekom Mitzvah.

Explanation: Even though we conclude that also to forbid the Tzarah, we do not need a verse, even so the Tana taught "Potros", for he needed to teach the Isur of a Tzarah, since we never heard it anywhere;

However, the Isur Ervah [is known]. All the Arayos are taught in [a Mishnah in] Kerisus 2a.

We do not need to teach that she is forbidden b'Mekom Mitzvah, for this is obvious that an Aseh is not Docheh a Lav with Kares.

Question: The answers above require a verse for Ervah herself. What is their source to permit the Tzarah Lo b'Mekom Mitzvah?

Answer: They learn from Rebbi's source (below).

Explanation #1: We can say that we expound the extra "Hei" to teach about two marriages, like we expound in Kidushin (41a) v'Shilach- v'Shilchah to teach that a Shali'ach can make another Shali'ach.

Explanation #2 (Rashi): V'Lakchah connotes that two Yevamos fell to him, and the Torah teaches that he marries one, but not both of them.

Question: Perhaps we need the verse for this itself, when two Yevamos fell to him from one brother, that he may do Yibum with only one of them;

What is the source to expound that whenever there are two women he could take...?

Answer: We expound below (44a, that one may do Yibum with only one widow from one brother) from "[Asher Lo Yivneh] Es Beis Achiv" - he builds only one house, and not two houses.

Question: Perhaps the verse comes to teach that he does Yibum with the Tzarah, and not with the Ervah!

Partial answer: This is not difficult for the opinion that does not require a verse for the Tzarah.

Question #1: Also Chayavei Aseh should forbid the Tzarah, for we cannot say that he may marry either!

Question #2: Now, there is no Kares for Tzaras Ervah. If so, she should need Chalitzah, just like Chayavei Aseh, which we include below (20a) from "Yevimto"!

Answer #1: Chayavei Aseh are included to require Chalitzah, and they have a little Zikah, so they are included in v'Lakchah. (This answers Question #1);

Inference: If so, we are forced to say that Tzaras Ervah does not need Chalitzah. If she needed Chalitzah, she would be included in v'Lakchah! (This answers Question #2.)

Answer #2: V'Lakchah connotes that Kidushin takes effect on her. Therefore, Chayavei Aseh, on which Kidushin takes effect, are included in v'Lakchah. (This answers Question #1. Chasam Sofer - Tosfos means that in general, Kidushin takes effect on Chayavei Aseh. It is not clear whether Kidushin takes effect in Yibum of Chayavei Aseh. I ask that if it does not, Question #2 returns. Tzaras Ervah is just like Chayavei Aseh. For both of them, there is Kidushin only not b'Mekom Mitzvah! Rather, Tosfos means that Kidushin takes effect on Yibum of Chayavei Aseh, unlike Tzaras Ervah. This answers also Question #2 - PF.)

Citation (Yevamos 39a): We need this. One might have thought that he did the Mitzvah incumbent on him, and now she is forbidden to him with the Isur of Eshes Ach.

Question: This connotes that we do not need a verse to permit a second Bi'ah. What is the reason? The first Bi'ah fulfilled the Mitzvah incumbent on him;

Strengthening of question: The second Bi'ah does not override Chayavei Lavin, like it says below (20b).

Answer: We do not need a verse to permit a second Bi'ah, for this is logical. The Torah did not say to have Bi'ah with her to divorce her after the first Bi'ah.

Implied question: If so, this reasoning should permit a second Bi'ah also with Chayavei Lavin!

Answer: The second Bi'ah, is Reshus (optional so it is not Docheh the Lav). There is an Aseh only in the first Bi'ah.

Inference: This connotes that we expound the Hei.

Question: In Kidushin (14a), it connotes that we expound from the Hei that Bi'ah completes [acquisition] in a Yevamah, but [money or a document do] not...

Citation (14a) Question: We need v'Yibmah to teach that Yibum works b'Al Korchah!

Citation (cont.) Answer: If so (it came only for b'Al Korchah), it should have said v'Yibem. (Rather, it says v'Yibmah, to teach both of these.)

Answer: There the Gemara asks "if so, that it came to teach only that Bi'ah completes [acquisition], it should have said v'Yibem."

Support: The Gemara below (68b) is like this. It says "if so, the verse should say 'v'Hi b'Kodoshim Lo Sochel.'" (I.e. if it came to teach only about the matter taught previously, who disqualifies her. It does not mean "if it came to teach only about the last matter taught.)

Question: Below (19b), we expound from "v'Yibmah" that she still is considered a Yevamah from her first husband!

Answer (Rav Yitzchak): We expound these three Drashos from Yibem v'Yibem v'Yibmah. (Had the Torah written Yibem, we would expound one law. Had it written v'Yibem, we would expound two laws. It wrote v'Yibmah, so we expound three.)

Support: Similarly, in Kidushin (41a) we expound three Drashos from v'Shilchah - Shilach, v'Shilach, v'Shilchah.

Explanation: This excludes Chayavei Lavin. "And for Shogeg Chatas" excludes Pesach and Milah, for which there is no Chatas, like it says in Kerisus (2a);

"And for idolatry, one is liable only for something punishable with Kares for Mezid" excludes hugging and kissing. "And Chatas if Shogeg" excludes something without an action.