1) THE SOURCE FOR THE PRINCIPLE OF "MATNAS SHECHIV MERA"
QUESTION: Rebbi Zeira says in the name of Rav, "What is the source in the Torah that a Shechiv Mera's [verbal command, without an act of Kinyan, to make a] transaction is binding? It is derived from [the extra word in the verse], 'v'Ha'avartem' (Bamidbar 27:8)." Rav Nachman in the name of Rabah bar Avuha derives it from the extra word, "u'Nesatem." The Gemara explains why each one rejects the other's derivation.
The Gemara implies that both Rebbi Zeira and Rav Nachman maintain that the principle of Matnas Shechiv Mera (i.e. that the verbal instruction of a Shechiv Mera to give a gift is binding) is mid'Oraisa. In the Gemara later (147b), however, Rava quotes the opinion of Rav Nachman that a Matnas Shechiv Mera is an enactment of the Rabanan which was made in order to calm the Shechiv Mera and give him the assurance that his instructions will be carried out. The Rabanan gave a Matnas Shechiv Mera the efficacy of a Kinyan d'Oraisa.
How can these two contradictory statements of Rav Nachman be reconciled?
(a) The MAHARSHA (to Tosfos DH Minayin) answers that Rava there argues with the Gemara here. Rava maintains that Rav Nachman is of the opinion that a Matnas Shechiv Mera is mid'Rabanan. The Gemara here maintains that Rav Nachman understands it to be mid'Oraisa.
The Maharsha explains that this is why the Gemara there says, "v'Rava Amar Rav Nachman," meaning, "and Rava says that Rav Nachman maintains...," as opposed to, "Amar Rava Amar Rav Nachman." If the Gemara had used the phrase "Amar Rava Amar Rav Nachman," it would have implied merely that Rava quoted a statement of Rav Nachman. The phraseology of "v'Rava Amar," however, indicates that Rava argues with something that was said before.
(b) TOSFOS answers that Rav Nachman indeed maintain that a Matnas Shechiv Mera is only mid'Rabanan. When Rav Nachman says that it is derived from the verse of "u'Nesatem," he means merely that the verse is an Asmachta, a scriptural support for the enactment of the Rabanan, but it is not actually a Halachah d'Oraisa. (The Maharsha suggests that Tosfos had the Girsa of "Amar Rava Amar Rav Nachman" in the Gemara on 147b; see (a) above. Indeed, that is the way Tosfos earlier (76b, DH Keni) and in Kesuvos (85b, DH ha'Mocher) cites the Gemara here, as the PNEI SHLOMO points out.)
Tosfos explains further that although Rav Nachman (and, presumably, Rebbi Zeira as well) quotes a verse merely as an Asmachta, but not as the actual source of the Halachah, it is not problematic that the Gemara asks why each Amora rejects the other's derivation. Tosfos quotes a similar Gemara in Moed Katan (5a) to prove that it is the style for the Gemara to question even why an Amora would reject another Amora's Asmachta. However, he does not explain why the Gemara seeks to be so precise in finding a verse as an Asmachta for the Takanah d'Rabanan.
It seems that Tosfos follows only one of the opinions found in the Rishonim with regard to the nature of an Asmachta.
The RAMBAM, RAMBAN, and TASHBATZ maintain that an Asmachta is merely a way to remember a Takanah d'Rabanan by finding an allusion to it in a verse. The law that the Rabanan established, however, is not actually the intent of the verse. It is called an "Asmachta" because the Chachamim "leaned" or "supported" their enactment on the verse as a mnemonic device.
In contrast, the RITVA in Rosh Hashanah (16b) explains that every Asmachta reveals the hidden intent of a verse. An Asmachta is a Halachah which Hash-m intended to teach as the law, but which He did not make obligatory. Rather, Hash-m gave the power to the Chachamim to decide whether or not to make it obligatory as a rabbinic law. The Ritva strongly rejects the view that an Asmachta is merely a mnemonic device.
Tosfos seems to agree with the Ritva's approach. If an Asmachta is a law that Hash-m included in the intent of the verse, it is important to determine which verse is the Asmachta. If, however, an Asmachta is merely a mnemonic device, then it does not matter which verse one uses for that purpose.
2) THE STRENGTH OF A DYING MAN'S WORD
OPINIONS: Rav Nachman quotes Shmuel, who states that a lender who sells a loan document (Shtar Chov) to a third party retains the power to forgo payment on the loan and nullify the borrower's debt to the third party. He further states that even if the lender dies, his heir is able to cancel the debt as well. Rav Nachman himself states that there is an exception to this rule when a dying man gives away a Shtar Chov as a Matnas Shechiv Mera. In such a case, when the benefactor dies, his heirs cannot cancel the loan.
This law requires explanation. Why should any person have the right to negate a loan he sold to someone else, and why is a Shechiv Mera different?
(a) The RID and RI'AZ explain that in general a lender who sells a loan retains the right to forgo it because his sale of the document gives the buyer only the power to collect the loan but not the ownership of the money itself. A loan is given to be used (Milveh l'Hotza'ah Nitnah) and the money, therefore, is too intangible to be transferred to a third party. Since the original lender retains the ownership of the actual money, it is within his ability to forgo the loan after its sale. A dying man's present is different, as he gives over all his rights in this world. Just as his verbal instructions effect a transaction even though they are intangible, he can also give over intangible rights.
(b) TOSFOS, the ROSH, RASHBA, and RAN explain that the sale of a loan document is effective only mid'Rabanan, while a borrower's obligation to pay the lender is mid'Oraisa. (This is in contrast to the opinion of RABEINU TAM, who says that the sale of a loan document is also mid'Oraisa.) Therefore, even when a person sells a loan, he still owns the loan according to the Torah and he may forgo it. A deathly ill person is different because the validity of his transaction is derived from the Parshah of inheritances, and his transactions therefore have the efficacy of Torah transactions. As a result, the real heirs of a Shechiv Mera have no more power than the person to whom he sold the loan (who is also like an heir), and that is why the Shechiv Mera's heir cannot forgo the loan.
(c) RABEINU CHANANEL explains that when a lender sells a loan, in general he may claim later that he had received payment before the sale and thereby negate the loan. (See Ri'az to Kesuvos 86b who explains that the lender would have to reimburse the third party.) As a result, he also has the ability to forgo the loan. A dying person is different because he distributes his belongings with precision, and it is assumed that he did not make a mistake and was never paid for the loan.