1) GIVING AWAY AN INHERITANCE BEFORE ONE RECEIVES IT
OPINIONS: Rav Asi states that in a case in which a Bechor chose to receive an ordinary share of a field together with his brother, and not a double portion, he thereby forgoes his rights to the double portion. Rav Papa maintains that the Bechor has relinquished his rights only to the double portion of that field, but he still receives a double portion of the rest of the estate. Rav Papi argues and maintains that the Bechor has shown that he does not want a double portion, and thus he has relinquished his rights to the double portion of the entire estate. The Gemara explains that the Machlokes between Rav Papa and Rav Papi is whether or not a Bechor is considered to have a share in the estate before the estate is divided among the heirs.
Does this Machlokes apply only to a Bechor, or also to an ordinary son? May an heir sell or give away his portion of the inherited estate before the estate is divided?
(a) The RASHBAM maintains that Rav Papa and Rav Papi argue only about the extra portion that a Bechor is entitled to receive. Only this portion may be sold or given away before the estate is divided, according to Rav Papi who maintains that "Yesh Lo l'Bechor Kodem Yerushah"; the Bechor owns his portion even before the estate is divided among the heirs. An ordinary son's portion of the inheritance, though, certainly cannot be sold before the estate is divided.
(b) TOSFOS (126b, DH Lo Asa) maintains that the opposite is true. The argument between Rav Papa and Rav Papi is only with regard to the special portion of the Bechor. The portion of an ordinary son certainly may be sold before the division of the estate according to both Amora'im.
HA'GA'ON RAV NAFTALI TROP (#192) explains that the Rashbam and Tosfos disagree with regard to the status of the estate before division. The estate before division is called, "Tefusas ha'Bayis." Tosfos maintains that the Tefusas ha'Bayis is considered like property owned by partners in a partnership; all of the brothers have a share of the estate, but it has not yet been clarified which heir owns which part of the property. Since each of the brothers own a share of the estate, he essentially is a partner in the ownership of the estate with his brothers, and thus he may sell or give away his own portion just as a partner may sell or give away his share of property owned in a partnership.
The Rashbam disagrees and maintains that heirs, before the division of the estate, are not comparable to partners. In a normal partnership, each partner owns only a portion of the property. In the case of Tefusas ha'Bayis, each heir owns the entire estate collectively with the other heirs. Since he does not own any specific portion by himself, but rather he owns the entire estate together with the other heirs, he may not sell or give away his portion. (Y. MARCUS)
2) A FIRSTBORN'S RIGHT TO DECLINE THE DOUBLE PORTION WHILE HIS FATHER IS ALIVE
OPINIONS: The Mishnah states that when one stipulates that "my firstborn son shall not inherit the double portion," his stipulation is not valid because it conflicts with the law of the Torah which entitles the Bechor to a double portion. The Gemara asks that this stipulation is one concerning a monetary matter, and such a stipulation is binding even when it conflicts with the law of the Torah. The Gemara answers that such a stipulation is binding only when it may be assumed that there is consent on the part of all of those who are affected by the stipulation. In this case, it cannot be assumed that the Bechor consents.
This seems to imply that if the Bechor explicitly expresses his consent, then he indeed relinquishes his right to his double portion. Does this mean that a Bechor may relinquish his right, during his father's lifetime, to receive the double portion of inheritance after his father dies?
(a) The RASHBAM (DH Hasam Ka Machlah) writes that the reason why the father's statement is not binding in this case is that the silence of the Bechor is not considered consent; he remains quiet merely in order to avoid angering his father. He does not have any intention to forgo his double portion. The Rashbam's words imply that if the Bechor explicitly consents to forgo his double portion, then his consent is valid and he does not receive the double portion.
The OR ZARU'A suggests that the Rashbam maintains that only a Bechor can forgo his double portion, but an ordinary son cannot forgo his portion. This is because the Torah refers to the Bechor's double portion as a "gift" (see Insights to Bava Basra 124:1). Since a person is entitled to decline a gift, the Bechor is entitled to decline the double portion. An ordinary heir, in contrast, cannot decline his share, because doing so would be counter to the Torah's law of Yerushah. (See also KOVETZ SHI'URIM #403.)
The KETZOS HA'CHOSHEN (278:13) explains that, according to the Rashbam, the Bechor's right to forgo his double portion applies not only when his father says that he does not want the Bechor to receive the double portion, but even when the Bechor, on his own initiative, declares that he does not want the double portion. This is because the mechanism by which the Bechor is able to forgo his double portion is through Mechilah; a person can be Mochel and forgo something that he is entitled to receive. The NESIVOS HA'MISHPAT, on the other hand, explains that the Bechor cannot forgo his double portion; the Torah requires that he receive it as an inheritance. Only when the father of the Bechor says that he does not want the Bechor to receive the double portion, and the Bechor consents, does the Bechor not receive the double portion. This is because the father has the right to re-direct the inheritance to any of his heirs. Even though the Torah prohibits him from re-directing the double portion away from the Bechor, when the Bechor consents the Torah's prohibition is removed and the double portion can be re-directed by the father. When the father does not re-direct the double portion, though, and the Bechor declares that he wishes to forgo the double portion, he cannot forgo the double portion that the Torah gives him.
(b) The RASHBA and other Rishonim argue and maintain that a Bechor cannot forgo his right to the double portion while his father is alive. The Torah gives the property to the Bechor when his father dies, and until that time there is nothing that the Bechor can do to stop the Torah's law from taking effect.
(The RAMAH explains that the son's right to receive the inheritance comes at the moment that he is born. At that moment, he did not renounce that right, and thus the Torah's law takes effect and he receives the Yerushah and he cannot decline it.)
The Rashba adds that the Gemara, when it says that the Bechor did not consent, does not mean that if he did consent his consent would be valid. Rather, the Gemara means that the Bechor cannot consent to forgo his double portion, and even if he does consent, his consent is not valid. This is also the explanation of the NIMUKEI YOSEF here (see also TOSFOS to Kesuvos 56b).