(R. Yochanan or R. Elazar): If a Kohen Gadol did Yibum with a widow, the Tzarah is exempted.

(The other of R. Yochanan and R. Elazar): She is not exempted.

If she was widowed from marriage all agree that she does not exempt the Tzarah, for an Aseh does not override an Aseh and a Lav;

They argue about a widow from Kidushin.

One opinion says that she exempts the Tzarah, because an Aseh overrides a Lav;

The other opinion says that she doesn't exempt the Tzarah. The Aseh doesn't override the Lav, since Chalitzah could be done.

Question (Beraisa): If they did Yibum, he acquires her.

This shows that the Aseh overrides the Lav. It refutes the opinion that the Tzarah is not exempted.

Suggestion: This refutes Reish Lakish (who says that when it is possible to fulfill both, the Aseh doesn't override the Lav).

Rejection: No. Chalitzah is not considered a fulfillment of Yibum.

Question (Rava): Where does the Torah hint at Sheniyos?

Answer #1 (Rava): "Kol ha'To'evos ha'El (harsh)" implies that other sexual abominations are lighter, i.e. Sheniyos.

Question: What is the source that "ha'El" means harsh?

Answer: "He took Eilei (the strong ones) of the land".

Suggestion: Rava disagrees with R. Levi.

(R. Levi): The punishment for unjust measures is harsher than for Arayos.

Regarding measures it says "ha'Eleh". Regarding Arayos it says "ha'El"; the former is harsher.

Question: It also says "ha'Eleh" regarding Arayos!

Answer: That teaches that there is Kares for Arayos, but not for unjust measures.

Question: Why are measures stricter?

Answer: One can do proper Teshuvah for Arayos (if he did not father a Mamzer), but not for having cheated with unjust measures (he does not know to whom to return the money).

Answer #2 (Rav Yehudah): Sheniyos are hinted at in "He made handles, investigated and enacted many parables".

(Ula): Before Shlomo, the Torah was like a basket without handles (safeguards against sin). Shlomo made handles for it.

Answer #3 (R. Oshaya): "Go away; do not pass through (increase Isurim mid'Rabanan to keep people far from transgressing the Torah itself). Veer away, then pass."

(Rav Ashi): There is a parable for R. Oshaya's teaching. If a man has an orchard and he guards it from the outside, it is totally guarded. If he guards it from the inside, what is in front of him is guarded, what is in back of him is not guarded.

Rejection: This parable is inaccurate! If one guards from the inside, at least what is in front of him is guarded. Without Sheniyos, people would stumble in Ervah itself!

Answer #4 (Rav Kahana): "U'Shmartem Es Mishmarti" - make something to guard for My guarding.

Question (Abaye): If so, Sheniyos are mid'Oraisa!

Answer (Rav Yosef): It is mid'Oraisa, but Chachamim explained it.

Objection (Abaye): Chachamim explain the entire Torah!

Retraction: Rather, Sheniyos are mid'Rabanan; the verse is only an Asmachta.

(Beraisa): These are the Sheniyos: a man is forbidden to his two grandmothers (the mothers of his mother and father), the wives of his two grandfathers, the wives of his father's maternal brother and his mother's paternal brother, and the daughters-in-law of his son and daughter;

A man may marry the (ex-)wives of his father-in-law and stepson;

He may not marry his stepson's daughter. A stepson may marry the (ex-)wife or daughter of his stepfather.

His stepson's wife says to him 'I am permitted to you, but my daughter is forbidden to you.'

Question: The Torah forbids his stepson's daughter! "(Do not marry) the daughter of her (your wife's) son or daughter..."

Answer: Indeed, the Torah forbids her. The Tana wanted to teach 'His stepson's wife says to him, I am permitted to you, my daughter is forbidden to you'. I.e. even though her daughter is forbidden mid'Oraisa, Chachamim did not decree against her;

To teach this saying in the Seifa, the Tana needed to teach the Isur of the stepson's daughter in the Reisha, even though it is not Sheniyos.

Question: His father-in-law's wife can also say that 'I am permitted to you, but my daughter is forbidden to you', since she is Achos Ishto!

Answer: The daughter of his stepson is permanently forbidden to him, so it was taught. His father-in-law's wife is forbidden only in the life of his wife, so it was not taught.

(Rav): In most cases, when a relative is forbidden, Chachamim forbade all similar relatives in prior or later generations. There are four relatives for which the Isur does not extend.

Rav was sure about three of them - the wives of one's mother's paternal brother and his father's maternal brother, and his daughter-in-law;

Ze'iri added the wife of his mother's father.

(Rav Nachman bar Yitzchak): A way to remember this is (Ze'iri added) 'what is (a generation) above (his mother's paternal brother's wife, one of the Sheniyos of) Rav.'

Question: Why didn't Rav list this case?

Answer: It can be confused with the wife of the father's father. (We are adamant to forbid all generations above the father's father's wife, lest people permit the father's wife, which is an Isur Torah.)

Ze'iri is not concerned for this. A man is frequent in his father's house, so he will not err. He is infrequent in his mother's house, so he may err.

Question: A daughter-in-law is a Torah Isur! (Why did Rav list it among Sheniyos?)

Correction: Rather, he refers to the daughter-in-law of his son.

Objection: His son's daughter-in-law is not a limited Isur!

(Beraisa): One's daughter-in-law is Ervah. His son's daughter-in-law is a Sheniyah. This applies to the daughter-in-law of his son, and of his son's son, and of his son's son's son for all generations.

Correction: Rather, he refers to his daughter's daughter-in-law.

(Rav Chisda, citing R. Ami): The daughter-in-law was only prohibited because of the daughter-in-law.

Rav Chisda: Before I was a Chacham, astrologers told me that I would be a Chacham. I reasoned that if I will be a great Chacham, I will explain R. Ami's teaching, If I will be a teacher of children, I will ask others to explain it.

(Rav Chisda): The daughter's daughter-in-law was forbidden only due to (concern lest one marry) the son's daughter-in-law.

(Abaye): We are concerned about cases like Bar Tzisai's daughter-in-law (both his son and daughter had daughters-in-law, and they could be confused).

Question: What is the law of the wife of the mother's maternal brother?

(The Torah forbids the wife of the father's paternal brother.) We decreed about the wives of the father's maternal brother and the mother's paternal brother, which have a paternal side. When there is no paternal side, we do not decree;

Or, do we decree in every case?

Answer (Rav Safra): The Isur when there is one paternal side is a decree. We do not decree to guard a decree!

Objection (Rava): In many cases we decree to guard a decree!

His mother is Ervah, and his mother's mother is a Sheniyah. We decree about his father's mother due to the mother's mother!

This is because they are all called grandmothers.

His father's wife is Ervah, and his father's father's wife is a Sheniyah. We forbid his mother's father's wife due to his father's father's wife.

This is because they are all called wives of grandfathers.

The wife of his father's paternal brother is Ervah; the wife of his father's maternal brother is a Sheniyah. We forbid the wife of his mother's paternal brother due to the wife of the father's maternal brother.

This is because they are all wives of his uncle.

The question remains, is the wife of his mother's maternal brother forbidden?

Answer (Rav Yehudah bar Shila): In Eretz Yisrael, they say that whenever the female is Ervah, they decreed that the wife of the corresponding male is a Sheniyah.

Objection (Rava): This is not always true! A mother-in-law is Ervah, but a father-in-law's wife is permitted (after she is divorced or widowed)!

The daughter of his mother-in-law is Ervah, but the wife of his mother-in-law's son is permitted!

The daughter of his father-in-law is Ervah, but the wife of his father-in-law's son is permitted!

His stepdaughter is Ervah, but his stepson's wife is permitted!

The daughter of his stepdaughter is Ervah, but the wife of his stepdaughter's son is permitted!

Conclusion: Surely, Rav Yehudah bar Shila came to include the wife of the mother's maternal brother (she is a Sheniyah, for she corresponds to the mother's maternal sister, who is Ervah).

Question: Why is this case different (than Rava's cases, in which they did not decree)?

Answer: This case involves only one Kidushin. Rava's cases involve two acts of Kidushin.

Question (Rav Mesharshiya): Are the paternal grandfather's sister and the paternal grandfather's brother's wife Sheniyos?

Since the generation below them is Ervah, we decree;

Or, since these are distant generations, we do not decree!

Answer (Rav Papi): The Mishnah lists the Sheniyos, and omits these cases!

Rejection: The Tana omitted cases.

Question: What else did he omit? (Surely, he would not omit just these!)

Answer: He also omitted the Sheniyos of R. Chiya (Daf 40b).

Ameimar permitted the cases that Rav Mesharshiya asked about.

(Rav Hillel): I saw the Sheniyos of Mar brei d'Ravna; there are 16.

Suggestion: These are the eight of our Mishnah, six of R. Chiya, and the two in question!

Objection: If so there are 17, for we concluded that the wife of the mother's maternal brother is forbidden!

Answer: These two (that Rav Mesharshiya asked about) are similar, so they are counted like one.