1) A FIRSTBORN'S RIGHT TO DECLINE THE DOUBLE PORTION
QUESTION: The Gemara teaches that if a man died owing money and his creditor produced a deed of debt to the heirs, the Bechor is required to give twice as much as his brothers towards the repayment of the debt. The Bechor, however, has another option. He is entitled to decline the double portion of the inheritance, and, consequently, he will not be obligated to pay a double share of the debt.
RABEINU TAM (cited by Tosfos DH v'Im) comments that this applies even in a case where the debt was not the father's, but rather the Bechor's debt, such as when the Bechor had taken a private loan for himself. By declining his right to receive the double portion, the Bechor will not have enough money to pay back his creditor. Even though the creditor will not be able to collect his money at all (the creditor cannot collect it from the other brothers since he has no claim against them), the Bechor is entitled to decline the double portion.
This Halachah seems to contradict the Gemara in Kesuvos (86a) which states that it is a Mitzvah to return a loan to a creditor, and that Beis Din can force the debtor to perform this Mitzvah. Why is the Bechor not forced to accept the double portion so that he can perform the Mitzvah of repaying his loan? How can Rabeinu Tam rule that the Bechor is entitled to forgo his double portion when he has a Mitzvah to pay back his creditor?
(a) The KETZOS HA'CHOSHEN (9:1) answers based on the Gemara's explanation of the verse, "... to give him a double portion" (Devarim 21:17). The Gemara explains that this verse means that the firstborn's share is a gift that the Torah gives him ("Lases Lo"). The SHULCHAN ARUCH (CM 278:10) quotes the RA'AVAD (see also RASHBA and RITVA) who rules that since the double portion is a gift, the Bechor is entitled to refuse it, and if he does refuse it, he immediately loses his rights to it. If he later regrets forfeiting it, he cannot get it back.
Therefore, even if the Bechor owes money to a creditor, Beis Din is not able to force him to receive the double portion, because as soon as he renounces his rights to receive the Torah's gift, it is lost and cannot be retrieved.
(b) The KOVETZ SHI'URIM (#377) answers that there are limits to what a debtor is obligated to do in order to procure sufficient funds to repay his debt. Just as a debtor is not obligated to collect money from charity in order to repay his creditor, a debtor also is not obligated to receive presents in order to repay his creditor. The Torah calls the double portion of a Bechor a gift, as mentioned above, and thus the debtor is not obligated to receive it in order to repay his debt. (Y. MARCUS)
2) MONEY OWED TO AN ESTATE
QUESTION: The Gemara (124a) states that according to Rebbi, if the brothers inherited from their father a Shtar Chov, a contract attesting to a debt that someone owes him, the Bechor receives a double portion of the loan repayment. The RASHBAM (DH Yarshu) explains that this is because the Shtar is considered equivalent to the "Guf," the body of the property, and the money of the loan is considered like a profit that automatically accrues from that property. Rebbi maintains that the Bechor receives a double portion of the profits that come automatically from the estate after the father dies and before the estate is divided. The Rashbam adds that according to the Chachamim, the firstborn does not receive a double portion from the money of the loan repayment.
TOSFOS (DH Ein) questions the Rashbam's explanation. If a Shtar is considered like the "Guf" of the property, then why do the Chachamim maintain that the Bechor does not receive a double portion? The Shtar should be divided among the brothers and the Bechor should receive a double portion of the Shtar. Once the Bechor has a double share of the Shtar, he automatically receives a double share of the profits that come later! Tosfos explains that once the estate has been divided, any profits which accrue afterwards belong to the owner of the "Guf" of the property, even according to the Chachamim. The MAHARAM explains that Tosfos' question on the Rashbam is that since, according to the Chachamim, the Bechor does not receive a double portion of the money of the loan repayment, this proves that the Shtar is not the body of the property but rather just a piece of paper which gives the bearer the right to collect the loan, in contrast to the assertion of the Rashbam.
If the Shtar is considered like the "Guf" of the property according to the Rashbam, then why does the Bechor not receive a double portion of the money of the loan repayment, as Tosfos asks?
ANSWER: The KETZOS HA'CHOSHEN (278:6) answers that the Rashbam might follow the view of the TESHUVOS HA'RASHBA (3:137) who says that Beis Din does not divide a Shtar Chov which is in the possession of partners, because a Shtar is "Ein Gufo Mamon" -- a Shtar is not considered to be tangible property which Beis Din is capable of dividing. Rebbi, though, maintains that before the distribution of the estate, the Bechor receives a double portion from any profit that accumulates automatically, and therefore the Bechor receives a double portion from the loan returned by the debtor.
In contrast, according to the Chachamim -- who maintain that before the estate is divided the Bechor does not receive a double portion of profits that come automatically -- a Shtar is never divided, and thus the situation is always considered as though it is before the division of the property. Therefore, according to the Chachamim, the Bechor does not receive a double portion from the loan paid back to the estate. (Y. MARCUS)