1) HALACHAH: A HEALTHY MAN WHO REDIRECTS HIS INHERITANCE
OPINIONS: Rava asks whether Rebbi Yochanan ben Berokah's principle -- that a person may bequeath as much of his estate as he wants, as an inheritance, to one of his heirs (who is fit to inherit him) -- applies only to a Shechiv Mera, or whether it also applies to a Bari, a healthy person. Perhaps only a Shechiv Mera is able to redirect the inheritance, because he is preparing to die and the verse, "On the day that he bequeaths to his sons" (Devarim 21:16), applies, since he is expressing his final will concerning his estate. The verse does not apply to a Bari, though, and thus perhaps a Bari is not able to redirect the inheritance. The Gemara cites proof from an exchange between Rebbi Nasan and Rebbi that shows that a Bari is able to redirect inheritance among his sons. From the fact that the Chachamim instituted that Kesuvas Benin Dichrin (see Background to the Daf) be written in the Kesuvah as an inheritance, redirecting part of the Bari's estate to particular sons (such that the sons cannot collect the additional money from Nechasim Meshubadim, like a Ba'al Chov, but only from Nechasim Benei Chorin, like an inheritance), it is clear that a Bari is also able to redirect the inheritance of his estate, according to Rebbi Yochanan ben Berokah.
The Gemara seems to conclude that a Bari may instruct who shall inherit what parts of his estate as an inheritance and not merely as a gift. Is this the Halachah?
(a) The RASHBAM (DH u'Shema Minah, and 131b, DH l'Olam) explains that the Gemara's resolution of this question is conclusive, and a Bari may dictate the terms of the inheritance. This is also the view of the RI (cited by Tosfos) and the BA'AL HA'ME'OR.
(b) Other Rishonim, including TOSFOS, the RIF, ROSH, RAMBAN, and TUR, maintain that the Gemara does not resolve this question. Accordingly, a Bari may not dictate the terms of the inheritance. This is the Halachah as recorded by the SHULCHAN ARUCH (CM 381:5).
Tosfos explains that the Gemara's inference (that a Bari may redirect the inheritance of his heirs) from the exchange between Rebbi Nasan and Rebbi is not conclusive, because perhaps that ruling applies only in the case of Kesuvas Benin Dichrin. The Chachamim enacted that a man is able to redirect part of his estate to his sons (from one mother) for the benefit of those sons and their mother. In all other cases, however, a Bari cannot dictate the terms of his sons' inheritance. (See Tosfos' explanation of the flow of the Gemara.)
The NIMUKEI YOSEF maintains that not only can a Bari not dictate the terms of the inheritance, but even if he attempted to do so and the beneficiary of his terms seized the portion that the Bari designated for him, Beis Din takes it away from him.
The HAGAHOS ASHIRI cites the opinion of the OR ZARU'A who maintains that even though the Gemara does not resolve its question (as Tosfos explains), if the beneficiary of the terms seized the portion designated for him, Beis Din does not take it away from him. Since the matter is in doubt, he is able to argue that he is certain that a Bari is empowered to dictate the terms of the inheritance. This is also the opinion of the RA'AVYAH.
The SHACH (in TAKFO KOHEN #72) asks that the Ra'avyah elsewhere maintains that, in general, when the Gemara leaves a question unresolved, one who seizes the item in question on the grounds that he is certain that the Halachah is in his favor is not entitled to keep the item, and Beis Din takes it away from him. Why, then, in this case, does the Ra'avyah allow the person who seized the property to keep what he seized?
The Shach suggests that the Ra'avyah is of the opinion expressed by the MAHARSHAL, who writes that only when the Gemara leaves its question unresolved with the word, "Teiku," is seizing the object ineffective. When the Gemara does not end with "Teiku" but rather it merely does not answer its question, one who seizes the item in question and argues that he is certain that the Halachah is in his favor may keep the object.
The TUMIM notes that the Shach himself maintains that whenever there is a dispute among the Poskim about what the Halachah is, if one of the litigants seizes the item in question and claims that he is certain that the Halachah follows the opinion of those Poskim who rule in his favor, he may keep the item. Accordingly, in the case of the Gemara here in which some Rishonim (the Rashbam and the Ri) maintain that the Gemara resolved its question and a Bari indeed may alter the inheritance, if the beneficiary of the Bari's terms seizes his portion he may keep it and Beis Din cannot take it away from him. (Y. Marcus)

131b----------------------------------------131b

2) MAKING ONE'S SON A CARETAKER OF THE ESTATE
OPINONS: The Mishnah (130a) teaches the ruling of Rebbi Yochanan ben Berokah, who says that one may redirect his estate to any one of his heirs as he chooses. The Gemara here assumes that one who gives all of his property to one of his sons merely intends to make that son an Apotropos, a manager to take care of the estate, so that his other sons will respect him and his decisions. He does not intend to give the son actual possession of the property.
What determines whether the beneficiary actually receives possession of the property or whether he merely becomes a caretaker of the property?
(a) The RASHBAM (130a, DH Halachah) maintains that whenever the father stipulates that the son should "inherit" him, the son becomes the actual owner of the property. By saying that he wants his son to "inherit" the property, he implies that he wants the son to own it in the same way that he himself owns it. It is only when the father stipulates that he wants to give his son a "gift" that we assume that he does not intend to grant his property to the son, but rather he intends only to appoint his son as the caretaker over the property. It is likely that when he expressed his will to give the property to his son, he intended that the property should be under his son's control, but not in his ownership. (Accordingly, it does not matter whether the father communicated his will in writing or orally, or whether he included all of the estate or part of the estate in the gift.)
(b) RABEINU CHANANEL (cited by the ROSH 8:31) maintains that only when one orally dictates his will does the son take possession of the estate, but when one puts his will in writing he only makes his son a caretaker of the property. The ROSH disputes this view, because he does not agree that the son should lose just because the will was written (a written statement of intent is usually stronger than a verbal one). He suggests that perhaps Rabeinu Chananel means that since it can be assumed that the written word becomes more well-known than the spoken word, when the father wrote his will it is likely that he meant merely to publicize his high regard for his son so that others would honor him as well.
(c) The Rosh cites another explanation in the name of Rabeinu Chananel. It is assumed that when only part of the estate was given to one son, the father intended for him to own what he gave him, but when the entire estate was given, he intended to make the son a caretaker over the estate.
(d) The ROSH explains simply that it is always assumed that the father wants to make his son a caretaker of the estate unless he specifies that he intends that his son actually own the estate.
(e) The BA'AL HA'ME'OR maintains that it is assumed that the father intended to make his son a caretaker of the estate only when the other sons are minors, or when they are overseas. In such a case there is a practical need for a caretaker. In all other cases, the son actually becomes the owner of the estate. (Y. Marcus)