1) GIVING A DOWRY
QUESTION: When Rav Papa invited Rav Yehudah bar Mereimar to accompany him to the negotiations for the Nedunya for his son, Rav Yehudah declined. Rav Papa prodded him to come, telling him not to think that it is prohibited to give a Nedunya to one's daughter for one thereby causes that money to be taken away from the inheritance of the sons. On the contrary -- the Rabanan instituted that one should give a Nedunya to his daughter, as we find that Rebbi Yochanan said in the name of Rebbi Shimon bar Yochai that the Rabanan instituted the "Kesuvas Benin Dichrin" -- that the Kesuvah of the mother goes to her children after her death -- in order to persuade a man to write a large Nedunya for his daughter.
Why did Rav Papa mention the Takanah d'Rabanan of "Kesuvas Benin Dichrin" as proof that one may give his daughter a Nedunya? The Gemara earlier (52b) points out that it has a source in the Torah! The prophet tells the Jewish people, after the Churban, that Hash-m wants them to acquire husbands for their daughters, as the verse says, "One should acquire husbands for his daughters [by giving them a large Nedunya]" (Yirmeyahu 29:6). Why, then, did Rav Papa quote Rebbi Yochanan's statement about the Takanah d'Rabanan? He should have quoted the verse which teaches that one should give a Nedunya to one's daughter! (MAHARSHA, MITZPEH EISAN)
ANSWER: Rav Papa perhaps wanted to prove that not only is it permissible to give a Nedunya to one's daughters, but that it is a Mitzvah to give a Nedunya to one's daughters, even when one does not need to do so in order to find a Shiduch for her. Rav Papa was the father of the groom and had already decided to give his son in marriage to his wife's sister. The Nedunya, then, was not necessary to persuade Rav Papa's family to agree to the Shiduch. From the verse we do not see that one should give a Nedunya under such circumstances. The Rabanan, though, instituted that there should always be a respectable Nedunya. (M. Kornfeld)
2) REDIRECTING ONE'S INHERITANCE
QUESTION: The Gemara mentions Shmuel's teaching that it is improper for a person to give all of his possessions to one child and not let it be split equally among all of his children, even if one of his children is "bad." Why, then, did Avraham Avinu, in his lifetime, give all of his possessions to Yitzchak (Bereishis 25:5-6)? He left nothing for Yishmael and left only gifts to the children of his Pilagshim before sending them away!
ANSWERS:
(a) Yitzchak's situation was different, because Avraham was told in a prophecy that the only child that would be considered his descendant would be Yitzchak. (KLI YAKAR -- the RAMBAN also hints to this answer in Bereishis 25:6; see also MAHARSHA to Sanhedrin 91a.)
(b) The DA'AS ZEKEINIM (end of Parshas Chayei Sarah) writes that Yishmael was not considered a rightful heir of Avraham because Yishmael was Megayer after his birth, and a "Ger she'Nisgayer k'Katan she'Nolad Dami." Thus he was not Halachically related to Avraham.
As far as the children of the Pilagshim were concerned, those children were only born after Avraham Avinu had already given away everything to Yitzchak. He already gave his possessions to Yitzchak at the time that he married Rivka, as we see in the verse (Bereishis 24:36).
(c) RAV ELYASHIV (in He'oros b'Maseches Kesuvos) answers that we see from our Sugya that it is permissible to give a gift to one's daughter, even though it will then not be split among the sons, because there is a purpose to it -- it will help the girl get married. Accordingly, since Avraham Avinu gave all of his money to Yitzchak in order for Eliezer to be able to find him a proper wife, it had a purpose and it was certainly permitted to give all of his possessions to Yitzchak.
(d) RAV MOSHE FEINSTEIN zt'l (IGROS MOSHE, Choshen Mishpat II:50) writes that when the Gemara says that one should not take away one's possessions from one son and give it to another son, even from a bad son to a good son, it is only referring to a bad son who is slightly disrespectful towards the Torah, or a son who has bad character traits. If, however, the child is a heretic and desecrates Shabbos and is raising his children in his evil ways, then certainly a person is permitted to give his possessions to the son who observes the Mitzvos, and doing so is commendable. One does not have to take into account that perhaps his grandchildren from the other son will do Teshuvah, since it is unlikely and uncommon.
The TCHEBINER REBBE (in DOVEV MESHARIM 1:97) uses this to explain why Avraham Avinu gave all of his possessions to Yitzchak. The other children were clearly not going to grow up to be Shomer Mitzvos and their children would not be part of the Jewish people.
3) WHY A WOMAN SHOULD LOSE THE "KESUVAS BENIN DICHRIN"
QUESTION: The Gemara discusses whether a woman who forgoes her Kesuvah to her husband also loses the Kesuvas Benin Dichrin if she dies before her husband dies. The Gemara asks that perhaps she loses it because she belittled the Kesuvah by forgoing it.
Why should the woman's Mechilah of the Kesuvah cause her to lose the Kesuvas Benin Dichrin? The Mishnah (54b) tells us that a man is not allowed to remain with his wife if there is no Kesuvah, even when the woman was Mochel the Kesuvah or lost it (57a), and a new Kesuvah must be written in order for them to be permitted to continue living together. Consequently, since they must rewrite the Kesuvah, she should get the Kesuvas Benin Dichrin from the new, re-written Kesuvah!
ANSWERS:
(a) The RIF (Teshuvah #42) cited by the RITVA explains that the Gemara means that she was Mochel the Kesuvah immediately before she died, and no new Kesuvah was written.
(b) The RASHBA understands the Rif differently. He says that the Rif's answer is that she was Mochel her rights to the Kesuvah in the event of her husband's death, but she was not Mochel her rights to the Kesuvah in the event of divorce. Since the only reason a man's wife must have a Kesuvah is so that she not feel that the husband can divorce her at whim, here there is no need to write a new Kesuvah after her Mechilah, because the original Kesuvah remains in force as far as divorce is concerned. Therefore they are allowed to remain together.
(c) The RASHBA, RA'AVAD (cited by the Rashba), RITVA and others answer that the Gemara's case is where she forgoes the Kesuvah and she writes a new Kesuvah, but she does not include in the new Kesuvah the Kesuvas Benin Dichrin. Since she belittled the Kesuvas Benin Dichrin by being Mochel the first Kesuvah which contained it, she is not entitled to the Kesuvas Benin Dichrin when she writes the Kesuvah anew.
The Rif, who does not accept this answer, might have learned that she only loses the Kesuvas Benin Dichrin as a penalty for belittling the Kesuvah itself (by expressing a desire to remain with her husband without a Kesuvah), and not just for belittling the Kesuvas Benin Dichrin. If she is only Mochel the Kesuvas Benin Dichrin, but she still keeps a Kesuvah, then she still gets the Kesuvas Benin Dichrin.