The Gemara then cites another Beraisa in which Beis Hillel says that both on
Shabbos and on a weekday it suffices for the husband to be Mevatel the Neder
in his heart and he does not have to articulate his Hafarah verbally.
How can Beis Hillel and Rebbi Yochanan say that the husband may be Mevatel
the Neder in his heart? The Gemara later (79a) says that even though Hakamah
is effective when done in one's mind, Hafarah must be articulated verbally!
In addition, why does Beis Hillel say that a husband may simply be Mevatel
his wife's Neder in his heart, when the previous Beraisa states explicitly
that he must also say, "Take the item and eat," which teaches that it does
not suffice to be Mevatel the Neder in his heart!
(a) The ROSH and TOSFOS in one explanation say that Hafarah indeed can be
done in one's mind, just like Hakamah. (See the Gemara on 76b where the
Gemara mentions a Hekesh between Hakamah and Hafarah.) When the Gemara later
says that Hafarah cannot be done in one's mind, it means that it does not
suffice to mentally *want* to be Mefer, but one must *say* the words in his
mind, "It is annulled for you" ("Mufar Lechi") (see the Rosh's comments on
this). (See also Insights to Berachos 15:1b.)
The second Beraisa in which Beis Hillel says that it suffices to be Mefer in
one's heart means that although the Hafarah is accomplished through what the
man thinks in his mind, nevertheless he must tell his wife that she should
take and eat the food, in order to inform her that he has been Mefer the
Neder. By telling her in this manner, he prevents slighting the honor of
Shabbos.
(b) The ROSH in the name of RABEINU ELIEZER MI'MITZ explains that when Beis
Hillel and Rebbi Yochanan say that one may be Mefer the Neder in his heart,
they mean that he must verbalize the Hafarah, but he may say it so quietly
that only he can hear it.
Beis Hillel does not mention that the husband must tell his wife to take the
item and eat it, since that is not part of the Hafarah, but it is merely to
inform her that he has been Mefer and that she is allowed to eat it (as
mentioned in the previous answer).
(c) The RAN explains that even though Hafarah cannot be done in one's mind,
nevertheless if he says in his mind the correct wording of Hafarah *and* he
openly enunciates a statement denoting Hafarah but he does not use the
proper wording of Hafarah, then the combination of what he thought and what
he spoke is able to accomplish Hafarah.
The logic of the Ran's explanation might be that it is only necessary to
pronounce the Hafarah openly in order to make the Hafarah a stronger, more
deliberate decision, instead of being just a mere thought. Therefore, if he
says something that lets us know that he has been Mefer in his mind
("Machshavaso Nikeres mi'Toch Diburo") presumably with the correct formula,
then it suffices to let us know (in any wording) that his decision was
final.
According to the Ran, when Beis Hillel says that the husband may do Hafarah
in his mind, he means that his thoughts are effective for Hafarah as long as
he verbally articulates some indication of what is in his mind, even though
he does not articulate the formal wording of Hafarah.
It is not clear what the source would be for such a Hafarah without actually
speaking out the proper formula. Such a statement would seemingly not
suffice to make a Neder. Why, then, should it suffice for Hafarah?
Perhaps the Hafarah works because we assume that since Hakamah can be done
even in the mind without any speech, the requirements for Hafarah should not
be so completely different. Even if speech is necessary for Hafarah, it
should suffice for him to say something that lets us know that he was Mefer
in his mind.
(d) The RAMBAM (Hilchos Nedarim 13:4-7, and in Perush ha'Mishnayos, end of
this Perek) explains that there are two completely different methods for a
husband to use in order to remove his wife's Neder. The first method is
Hafarah, which cannot be done in the mind. The second method is "Kefiyah"
(lit. "forcing"), in which the husband tells his wife, "I want you to eat
the item that you prohibited upon yourself." Whether she actually eats it or
not, the fact that he was trying to force her to eat it removes her Neder
just like Hafarah does.
"Kefiyah" is a stronger method of removing a Neder, since he not only says
that he does not want her to have the Neder, but he protests it by
overriding the Neder and telling her to do what she said that she would not
do. Hafarah, on the other hand, merely shows that he does not want her to
have a Neder upon her, but not that he specifically wants her to do the
thing that she prohibited upon herself. Since "Kefiyah" is a strong form of
removal of her Neder, even if he merely thinks in his mind that he is going
to force her, it suffices to remove the Neder. This form of annulment in his
heart is referred to as "Bitul." (The Mishnah in Nazir (61a) mentions a
similar concept of forcing a slave to go against his Nezirus as a way for
the master to remove his slave's Nezirus. However, the Mishnah there says
that this method cannot be done with one's wife. See RA'AVAD on the Rambam,
ibid.)
According to the Rambam, why does Beis Hillel say that the husband may be
Mevatel the Neder in his heart without saying "take the item and eat?" The
Rambam (in Perush ha'Mishnayos) explains that Beis Hillel is discussing a
situation where the husband is not able to force her right now to do the
action (such as eat the food). In such a situation, it suffices for him to
think in his heart that he is Mevatel it. But if he can force her, then he
should force her *and* think in his heart that he is Mevatel the Neder.
The Rishonim reject the Rambam's explanation, since we find no source for
such a second method for a husband to repeal his wife's Neder. It is
possible that the Rambam found support for his ruling from the wording of
the verse, which uses two different words for repealing a Neder: "Hefer" and
"Heni."
The verse uses the word "Heni" when discussing a father removing his
daughter's Neder (Bamidbar 30:6). It uses the word "Hefer" when discussing a
husband removing his wife's Neder (30:12), and it uses both "Heni" and
"Hefer" when discussing an Arus removing, together with the father, a
Na'arah Me'urasah's Neder (30:9). According to the Rambam, the verse might
be mentioning the more common method of removing a Neder in each case.
"Heni," which is used with regard to the Hafarah of the father, perhaps
refers to the act of Bitul, or "Kefiyah," of the Neder, like Rashi on the
verse translates, "He refuses her Neder to her." A father normally removes
his daughter's Neder by "Kefiyah," since that is the nature of the
relationship between a father and daughter. A husband, on the other hand,
usually does not force his wife, but prefers to remove the Neder through
Hafarah, because of the nature of their relationship. Hence the Torah
mentions only "Hefer" with regard to a husband and wife. In the case of a
Na'arah Me'urasah, the girl is still young but somewhat independent, and
thus the Torah uses both "Heni" and "Hefer," because both methods of
annulment are common in that case! (M. Kornfeld)