Question: What is the source [to enact] Sheniyos?

Answer (Rav Huna): "[Ha'To'evos] ha'El" means harsh. This implies that there are [Arayos] less [severe] than them.

Note: There are Chayavei Lavim mid'Oraisa that are less severe than the Arayos written there, which have Kares! Perhaps since the Torah wrote "ha'El", as opposed to "ha'Eleh", which it normally uses (e.g. the previous verse), this hints to Chachamim to enact Sheniyos. The Torah need not hint that there are less severe Arayos in the Torah!

These are the Sheniyos - [a man is forbidden to] his father's mother, his mother's mother, the wife of his father's father, the wife of his mother's father;

The wife of his son's son, the wife of his daughter's son, the wife of his mother's brother, the wife of his father's maternal brother.

(R. Chanin - Beraisa): All of these [Sheniyos] have no limit (all generations are forbidden), except for the wife of his mother's father.

Bar Kapara says that all of them have a limit, for Bar Kapara added [to forbid] the mother of his mother's father and the mother of his father's father. (If he held that there is no limit, automatically these are forbidden!)

(Rav): The wife of his daughter's son has a limit.

Question: What is the difference? [Why does Rav not say the same about the wife of his son's son?]

Answer: The wife of his son's son comes from elsewhere (she married a descendant from pure paternal lineage. There is more reason to forbid, since sons inherit and are frequent with their fathers. This does not apply to the wife of his daughter's son. We explained this based on ROSH 2:1 and Hagahos HA'GRA there.)

(Rav): Seed that comes from him is forbidden to him.

(R. Yosi bei R. Bun): According to Rav, Avraham is forbidden to all women of Yisrael, and Sarah is forbidden to all men of Yisrael.

(Rav): Any [relative] that if [the relative] were female, she would be forbidden mid'Oraisa, if [the relative] is a male, his wife is forbidden;

His father's sister, a female, is forbidden; his father's brother, a male, his wife is forbidden. (The Chidush is for his father's maternal brother. The wife of his paternal brother is forbidden mid'Oraisa!)

His mother's sister, a female, is forbidden; his mother's brother, a male, his wife is forbidden.

His son's daughter, a female is forbidden; his son's son, a male, his wife is forbidden.

His daughter's daughter, a female is forbidden; his daughter's son, a male, his wife is forbidden.

(R. Yakov of the south, in front of R. Yosi): We find a decree due to a decree [regarding Sheniyos]! His mother is a Torah Isur. His mother's mother is a Sheniyah [forbidden due] to her. They forbade his father's mother due to his mother's mother!

His son's wife is a Torah Isur. The wife of his son's son is a Sheniyah [forbidden due] to her. They forbade the wife of his daughter's son due to the wife of his son's son!

(R. Masniya): We find a decree due to a decree [regarding Sheniyos]! His father's wife is a Torah Isur. The wife of his father's father is a Sheniyah [due] to her. They forbade the wife of his mother's father due to the wife of his father's father!

The wife of his father's paternal brother is a Torah Isur. The wife of his father's maternal brother is a Sheniyah [due] to her. They forbade the wife of his mother's maternal brother due to the wife of his father's maternal brother!

R. Chunah learned all of these from the following verse - "Ervas Ishah u'Vitah Lo Segaleh Es Bas Benah v'Es Bas Bitah... [Zimah Hi]" - we learn from a Gezeirah Shavah "Zimah-Zimah" (with "v'Ish Asher Yikach Es Ishah v'Es Imah Zimah Hi");

Just like below (descendants of his wife), the Isur is [up to] three generations (counting from her, i.e. her granddaughters), also above, it is three generations (her grandmothers);

Just like below, there is a Lo Sa'aseh, also above there is a Lo Sa'aseh;

Just like above, the Isur is through Nisu'in (if one raped or enticed a woman, there is no Isur to marry her mother or grandmother), also below it is through Nisu'in;

Just like above, [the punishment is] Sereifah (death through burning), also below it is Sereifah.

Just like below, the daughter of a male (her son) is like the daughter of a female (her daughter), also above, the mother of a male is like the mother of a female.

Explanation: What do we learn from this? [We forbid] the mother of his father-in-law and the mother of his mother-in-law. His father's mother should be no less [forbidden] than his father-in-law's mother! His mother's mother should be no less [forbidden] than his mother-in-law's mother! (These are not mere decrees. A Kal v'Chomer teaches that it is proper to forbid them!)

They forbade the wife of his father's father due to his father's mother. They forbade the wife of his mother's father due to his mother's mother. (They are not decrees due to decrees, like R. Masniya said above.)

The wife of his son's son should be no less [forbidden] than the daughter of his wife's son. The wife of his daughter's son should be no less [forbidden] than the daughter of his wife's daughter. (These are not decrees due to decrees, like R. Yakov of the south said above!)

Question (R. Chagai, to R. Yosi): A Beraisa argues with Rav [who said that any female relative forbidden mid'Oraisa, the corresponding male, his wife is forbidden]! It says that one is permitted to the wife of his step-son (his wife's son from another man), and forbidden to his [step-son's] daughter;

Is he not forbidden to his step-daughter (his wife's daughter)? Regarding a male (his step-son), his wife is permitted!

(R. Zerikan citing R. Chanina): The wife of one's father-in-law is forbidden due to Maris ha'Ayin (she looks like his mother-in-law);

If you will say that it is [a fence due to] Torah law, [this cannot be, for] David married Ritzpah bas Ayah (Sha'ul's wife) - "va'Etenah Lecha Es Beis Adonecha v'Es Neshei Adonecha b'Cheikecha"! (R. MEIR SIMCHAH - a king's widow may marry only a king. If Ayah could not marry David, she would be an Agunah (unable to remarry) forever. This is a reason to overlook concern for Maris ha'Ayin, but if it were a fence due to Torah law, concern for Agunah would not override it!) This is unlike the Bavli (Yevamos 21a) which says that Shlomo enacted Sheniyos (PF). If so, there is no question from David!)

(R. Yirmeyah citing R. Lazar): If two step-children grew up together in one house (the father of one married the other's mother), they may not marry each other, due to Maris ha'Ayin (they look like siblings).

A case came in front of R. Chaninah brei d'R. Avahu. He said, they should marry in a place where people do not know about them (that they grew up together. Once they are married, they may return to their place.)

Question: In a Mishnah (Kerisus 3:5), R. Yosi says 'if the elder transgressed and married (did Yibum, with his son's daughter-in-law)... 'What did he transgress?

Answer: He transgressed mid'Rabanan. (Mishnah 3 says that Isurei Mitzvah do Chalitzah, but not Yibum.)

Version #1 (R. Yosi, citing R. Avahu) Question (R. Lazar, to R. Yochanan): Does this [Mishnah cited above] teach that Sheniyos have no limit? (It could have said 'if he transgressed and married her...' Rather, it said 'if the elder transgressed...' to hint that the same applies if the grandfather married his son's son's daughter-in-law!)

Answer (R. Yochanan): Did we learn Sheniyah to Sheniyos?! We learned only Sheniyah to Divrei Torah. All of the Isurim are for his son's daughter-in-law (it does not discuss a grandfather who married his son's son's daughter-in-law).

Version #2 (R. Chizkiyah citing R. Yonah): R. Avahu did not say so! Rather, [he said that] R. Lazar asked R. Yochanan 'eight Sheniyos were taught', and this (Mishnah in Kerisus) teaches a ninth! (I.e. the daughter of the daughter of his son. If it were the daughter-in-law of his son, there was no need to say that he transgressed. Perhaps he married her before she was the daughter-in-law!)

[R. Yochanan answered, it does not discuss a grandfather. Bas Bas Beno is permitted. All of the Isurim] are for his son's daughter-in-law. (We explained this like HA'GAON RAV C. KANIEVSKY, SHLITA.)