1) INHERITING PROPERTY FROM ONE'S FATHER THROUGH HIS GRANDMOTHER
OPINIONS: The Gemara discusses a case in which a man gave his possessions to his grandmother, stipulating that after her death the possessions should be inherited by his heirs and not by his grandmother's heirs. The man's sole heir was his daughter, but she died during his grandmother's lifetime. The daughter's husband claimed that he was entitled to the estate.
The "Benei Ma'arava" asserted that if the daughter had been survived by a son, then he would have inherited the estate (in place of his mother). Her husband is not entitled to inherit the estate through his wife, because a husband does not inherit from his wife property that is "Ra'uy" -- property which was not in the possession of his wife at the time of her death but which will come later to his wife, after her death.
Rabah supports this view by reasoning that had the grandmother sold the possessions, the sale certainly would have been valid (even though she is not permitted to sell the property l'Chatchilah, as the Gemara teaches on 137a), and after the grandmother's death the property would not have reverted back to the heirs.
How does Rabah's proof support the ruling of "Benei Ma'arava"?
(a) The RASHBAM explains that Rabah means that it is not possible that the father intended to give his daughter the estate itself (Guf ha'Karka), reserving only the Peros (i.e. the rights to the produce of the property) for the grandmother. His proof for this is that had the grandmother sold not only the Peros but even the estate, the sale would have been valid. It is evident that the grandmother owns the field until her death, and the man's daughter would have inherited the property from her had the grandmother died first. A husband, though, does not inherit from his wife property that his wife would have inherited ("Ra'uy"). In contrast, the child of the deceased does inherit property that is "Ra'uy," and thus had the daughter been survived by a son he would have inherited that property.
(b) TOSFOS (DH l'Ta'amaihu) suggests that according to Rabah, the man actually intended to give the estate to his daughter, but he reserved the Peros for his grandmother. It is only because the grandmother can sell the estate that the daughter's ownership is considered insufficient as far as the husband is concerned, and that is why the daughter's husband does not inherit the estate from her.
The KOVETZ SHI'URIM (#392) points out that according to the Rashbam, since the daughter never owned the estate, her son would have inherited directly from his grandfather (his mother's father), and it would have been as if his grandfather had stipulated that the estate should go to his heir's heir. According to Tosfos, though, since the daughter did own the actual property (except for the rights to the Peros during the grandmother's lifetime), her son could have inherited the property from her. (Y. MARCUS)
2) HALACHAH: COLLECTING A DEBT OWED TO ONE'S DECEASED WIFE
OPINIONS: The Gemara says that when a woman dies, her husband does not inherit her property that is "Ra'uy," property which was not in the possession of his wife at the time of her death but which will come later to his wife, after her death.
When a married woman lends money and dies before she collects the debt, does her husband collect the loan from the debtor?
(a) TOSFOS (DH Amar Rav Papa) maintains that he is not entitled to collect money owed to his wife after her death, even when she lent money of her "Nichsei Melug" (of which the husband has the rights to consume the Peros).
(b) The ROSH (9:11) rules that in the case of the death of the wife, a husband generally may not collect loans owed to his wife, except when the money that she lent was from her "Nichsei Melug," property owned by the wife from which the husband is entitled to eat the Peros. Since the produce belongs to the husband, the money is considered to be in his possession, and she had no right to lend it out. Therefore, the husband collects the money even after her death.
(c) The MAGID MISHNEH (Hilchos Nachalos 1:11) cites the view of the RI MI'GASH who rules that a husband does collect loans owed to his wife after his wife dies. He asserts that the Rambam also seems to be of this opinion.
HALACHAH: The SHULCHAN ARUCH (EH 90:1) rules that a husband may not collect loans owed to his deceased wife. The BEIS SHMUEL there (#6) adds that since this is the opinion of the majority of Rishonim, even if the husband seizes the money from the debtor and claims that he is certain that the ruling of the Ri mi'Gash is correct, his claim is not accepted and he must return the money. (Y. MARCUS)