OPINIONS: The Gemara [Nedarim 15] discusses a case in which a husband attempts to prevent his wife from visiting her father's home by prohibiting her from any benefit from him until Pesach if she visits her father's home from now until Sukos. If she receives benefit from her husband before Pesach and, before Sukos, she goes to her father's home, the benefit she received from her husband retroactively becomes forbidden and the punishment of Malkus is administered.
Who is punished with Malkus when the wife transgresses the husband's Neder -- the wife or the husband?
(a) The RAN and most other Rishonim explain that the wife is punished with Malkus for having benefit from her husband. Since he made himself prohibited to her, it is as if he is Hekdesh to her, and thus she receives Malkus like one who receives personal benefit from Hekdesh.
(b) The Ran cites the RAMBAM (Hilchos Nedarim 5:1, 5:12) who argues and rules that the only one who is punished with Malkus for the violation of a Neder is the one who made the Neder. The verse says, "Lo Yachel Devaro" -- "he shall not profane his word" (Bamidbar 30:3); there is no Isur of Bal Yachel for violating someone else's word. Hence, the person who made the Neder will receive Malkus only if he helps the other person benefit from him in violation of his Neder. (See also Insights to Nedarim 35:2.)
Nevertheless, the Rambam writes that the wife is still forbidden from benefiting from her husband, even when he does not give her the benefit. She does not receive Malkus, though, if she benefits from him.
However, if "Lo Yachel Devaro" means that one may not violate his own word and only the person who made the Neder receives Malkus, why is the other person (the "Mudar Hana'ah") prohibited from violating the Neder?
The Rambam (Hilchos Ma'achalos Asuros 9:1) rules that the Torah prohibits one from deriving any benefit from a mixture of meat and milk, but it does not prescribe a punishment of Malkus for one who does (8:16). The reason is that the Isur against deriving benefit from a mixture of meat and milk is derive from a Derashah and is not written explicitly in the Torah, and Malkus is given only for an Isur written explicitly in the Torah (MAGID MISHNEH, Hilchos Ma'achalos Asuros 5:11).
Similarly, the Rambam may understand that since the simple meaning of "Lo Yachel Devaro" prohibits only the person who made the Neder from violating his word, and the Chachamim derived from a Derashah that a Neder creates an Isur Cheftza and makes the item prohibited to the Mudar, Malkus is not given to the Mudar if he violates the Neder. The Rambam maintains that the Isur Cheftza is what prohibits the Mudar Hana'ah from benefiting from the person who made the Neder, even though the Mudar Hana'ah did not make the Neder himself. No Malkus is given, however, since the Isur is not written explicitly in the Torah but is derived through a Derashah.
The Rambam (Hilchos Shevu'os 5:4, 6:7) writes that if a person makes a Shevu'ah prohibiting another person from performing a certain action with his object, the other person must abide by the Shevu'ah. The TUR (YD 238) asks, how can a person make an Isur Gavra on another person? One can make only a Neder, an Isur Cheftza, on his object, and prohibit it to another person. The KESEF MISHNEH writes that the Rambam does not mean that the "Mushba" (the person prohibited by the Shevu'ah from doing a certain act) will receive Malkus for violating the Shevu'ah, but rather that "the Shevu'ah takes effect on him partially" with regard to making the act prohibited. (See RADVAZ on the Rambam there, TAZ to YD 236, and BACH; see also KUNTRESEI SHI'URIM 4:12 of RAV YISRAEL ZE'EV GUSTMAN zt'l.)
The Rambam's logic may be that a Shevu'ah creates not only an Isur Gavra, but it also creates an Isur Cheftza, as Tosfos writes in Shevuos (25a). The Isur Cheftza, however, might not be any more severe than a normal Isur Cheftza created by a Neder, and therefore it creates only an Isur on the other person but not a Chiyuv Malkus.
The Acharonim point out that this approach may explain another ruling of the Rambam. The Rambam (Hilchos Shevu'os 2:8) rules like Rava (Shevuos 20a) that Hatfasah works for a Neder but not for a Shevu'ah. However, the Rambam (Hilchos Shevu'os 2:9) also rules that Hatfasah of a Shevu'ah does create an Isur, even though it does not create a Chiyuv Malkus (see BEIS YOSEF YD 239). Why does a Shevu'ah made with Hatfasah work to create an Isur?
The KEHILOS YAKOV (Nedarim #1) explains that the Rambam maintains that a Shevu'ah is able to create not only on Isur Gavra, but an Isur Cheftza as well. However, that Isur Cheftza is not punishable with Malkus, just like the Isur Cheftza of a Neder made on someone else. Therefore, if one is Matfis to that Isur Cheftza, he can create another Isur Cheftza which will take effect only with an Isur but not with a Chiyuv Malkus. (The Isur Cheftza is created even if he expresses the Shevu'ah in completely Shevu'ah-related terms, without referring at all to the object but only to the person.)
From the daf yomi advancement form - more to come bl"n and bez"H.
