QUESTION: The Mishnah states that one who makes a Shevu'ah that he will annul a Mitzvah is exempt from a Korban if he does not fulfill his Shevu'ah. Similarly, one who makes a Shevu'ah that he will perform a Mitzvah is exempt from a Korban if he does not perform the Mitzvah. The Mishnah says that logically he should be liable for such a Shevu'ah (in the case of a Shevu'ah to perform a Mitzvah; RASHI DH she'Hayah), based on Rebbi Yehudah ben Beseira's Kal va'Chomer that one is liable for violating such a Shevu'ah. His Kal va'Chomer states that if one is obligated to bring a Korban for not fulfilling a Shevu'ah to perform an optional action, which one did not obligated himself with a Shevu'ah at Har Sinai to perform, then one certainly is obligated to bring a Korban for not fulfilling a Shevu'ah to do a Mitzvah, which one obligated himself with a Shevu'ah at Har Sinai to perform.

Rebbi Yehudah ben Beseira's logic seems to contradict the principle of "Ein Isur Chal Al Isur" -- once an object is prohibited with an Isur Torah, it cannot become prohibited again with another Isur Torah. Why does Rebbi Yehudah ben Beseira say that a Shevu'ah to perform a Mitzvah takes effect, if this contradicts the principle of "Ein Isur Chal Al Isur"? (See TOSFOS DH Mitzvah.)

(One might attempt to answer that the principle of "Ein Isur Chal Al Isur" does not contradict Rebbi Yehudah ben Beseira's statement, because the Gemara in Chulin (113b) derives this principle from the verse that teaches the prohibition for a Kohen to eat Terumah when he is Tamei: "And they shall die for it, because the desecrated it" (Vayikra 22:9). The Gemara derives from this verse that if the Terumah has already become forbidden for a different reason (for example, it is Tamei), the Kohen who is Tamei is not obligated to bring a Korban for eating it. Therefore, perhaps "Ein Isur Chal Al Isur" applies only where it is taught by a specific verse. Since no verse teaches that a Shevu'ah does not apply to a Mitzvah, "Ein Isur Chal Al Isur" does not apply.

However, this does not resolve the contradiction, because even if a specific verse is needed to teach that "Ein Isur Chal Al Isur" applies, this principle still presents a Pircha (contradiction) to the Kal va'Chomer: how can Rebbi Yehudah ben Beseira derive a Kal va'Chomer from a Shevu'ah to perform a voluntary act to a Shevu'ah to perform a Mitzvah? Perhaps a Mitzvah is different because a Shevu'ah cannot apply to it because of "Ein Isur Chal Al Isur.")

ANSWER: The TOSFOS HA'ROSH answers that even Rebbi Yehudah ben Beseira agrees that a Shevu'ah not to transgress a prohibition (for example, "I will not eat Neveilah") does not take effect. He maintains only that a Shevu'ah to perform a positive Mitzvah (for example, "I will eat Matzah") takes effect.

The Tosfos ha'Rosh writes that the correct text in the Mishnah is the text which Rashi (DH she'Hayah) rejects. According to Rashi, the correct text in the second part of the Mishnah reads:

"If a person made a Shevu'ah to perform a Mitzvah and he did not perform it, he is exempt, even though logically he should be liable as Rebbi Yehudah ben Beseira says."

The text which Rashi rejects, but which the Rosh accepts, reads:

"If a person made a Shevu'ah to perform a Mitzvah and he did not perform it, he is exempt. These are the words of Rebbi Yehudah ben Beseira."

The Rosh explains this text as follows: "If one made a Shevu'ah to perform a Mitzvah (such as, "I will not eat Neveilah") he is exempt. Rebbi Yehudah ben Beseira explains, 'Logically, he should have been liable for this on the basis of the same Kal va'Chomer which, I maintain, obligates one to bring a Korban when he transgresses his Shevu'ah to fulfill a positive Mitzvah. Nevertheless, I agree that for this Shevu'ah he is exempt.' These are the words of Rebbi Yehudah ben Beseira."

The Rosh writes that according to this understanding of the Mishnah, the Gemara earlier (25a) must be interpreted slightly differently. The Gemara there says that when the Mishnah mentions a person who swears, "I will give to such and such," it cannot mean, "I will give charity to a poor person," because the person is sworn from Har Sinai to give charity. However, according to the Rosh's understanding of the Mishnah here, such a Shevu'ah would take effect according to Rebbi Yehudah ben Beseira. Rather, the Gemara there actually refers to the next part of the Mishnah which states, "I will not give," which even Rebbi Yehudah ben Beseira agrees is not a valid Shevu'ah. (D. BLOOM)

QUESTION: Rava rules that when one swears, "I will not eat this loaf," he transgresses his Shevu'ah as soon as he eats a k'Zayis of the bread. However, if he swears, "I will not eat it" (and he does not mention "this loaf"), he is not liable until he eats the entire loaf.

RASHI (DH ked'Rava) writes that the Shevu'ah, "I will eat," implies the entire loaf, while the Shevu'ah, "I will not eat," implies intention to prohibit to himself "Kedei Achilah," the amount of "eating," which is a k'Zayis. The RITVA adds that the only reason why the person mentioned "this loaf" is to permit himself to eat other loaves, but not to require him to eat the entire loaf.

What is the Halachah in the opposite case, in which the person swears, "I will eat this loaf"? How much of the loaf must he eat in order to fulfill his Shevu'ah?

(a) TOSFOS (29b, DH Shevu'ah) writes that when one says, "I will eat this loaf," his intention is to eat a k'Zayis just as he intends not to eat a k'Zayis when he says, "I will not eat this loaf." The RITVA adds that when he says, "I will eat," his intention is to obligate himself to eat a Shi'ur of Achilah, or a k'Zayis.

(b) The RITVA cites the RE'AH in the name of his teachers who maintain that one who says, "I will eat this loaf," must eat the entire loaf. The Re'ah explains that the reason for the difference between, "I will not eat," and "I will eat," is that when he says, "I will not eat," his intention is to prohibit himself from eating the bread, and since his intention is create a prohibition on himself, he presumably intends to prohibit even a small amount (a k'Zayis). In contrast, when he says, "I will eat," his intention is to obligate himself to do something that he was not previously obligated to do. Therefore, since he has taken a new obligation on himself, he presumably wants to take on the larger obligation (to eat the entire loaf).

The Re'ah adds that even when one swears, "I will not eat this loaf," the prohibition applies to every part of the loaf, because he will be liable for eating any k'Zayis of the loaf. (Therefore, just as "I will not eat" prohibits him from eating any part of the loaf, "I will eat," obligates him to eat the entire loaf.)

The Gemara later (28a) provides proof for this explanation. The Gemara there teaches that one who swears that he will not eat a loaf and then eats almost all of it, but leaves over a k'Zayis, may still rescind his Shevu'ah through She'eilah. The Gemara says that since She'eilah is effective for the last k'Zayis, it also is effective for the parts of the loaf that he already ate. The fact that one can do She'eilah on the last k'Zayis of the loaf proves that one who made a Shevu'ah to eat the loaf is prohibited from eating every k'Zayis of it.

The Re'ah asserts that according to this explanation, whether a person swears, "I will eat this loaf," or, "I will eat it," he is obligated to eat the entire loaf. (This contrasts with Rava's ruling that there is a difference between saying, "I will not eat this loaf," and "I will not eat it.")

However, the Re'ah adds that there may be a difference between "I will eat this loaf" and "I will eat it." When one says, "I will eat it," he obligates himself to eat it only if all of "it" is here, but if some of it becomes lost such that he cannot eat all of it, he automatically becomes exempt from eating any of it. In contrast, when he says, "I will eat this loaf," he must eat all of it if it is present, and if not all of it is present he must eat all of whatever is left of it. This is similar to the Shevu'ah, "I will not eat this loaf," where he becomes prohibited from eating every k'Zayis of it. If he says, "I will eat this loaf," he becomes obligated to eat every k'Zayis that he can.

The Re'ah rules similarly in another case. One swears that he will return to his friend a certain sum of money that he had borrowed from him. He finds that he is unable to return the full sum, but is able to return part of it. The Re'ah rules that his Shevu'ah obligates him to repay whatever he can. When he swore that he would return the money to his friend, he obligated himself either to repay the full amount or to repay part of it if he is unable to return it all. This is similar to the person who swore, "I will eat this loaf," who thereby obligated himself to eat every k'Zayis that he can.

This ruling is in contrast to the law in the case of a person who swears that he will go to a certain place. If he becomes unable to go to that place, he is not obligated to go part of the way, because no one derives any benefit if he goes part of the way. In contrast, a lender derives some benefit from receiving any part of the loan in return, and therefore the borrower is obligated by his Shevu'ah to return even a partial amount of the loan. (See also TAZ YD 238:11, and CHIDUSHEI GERSHONI and REBBI AKIVA EIGER there. See also footnote 490 to the Ritva.)

Tosfos (in (a) above) apparently concludes like the Ritva. Tosfos writes, "It is possible that there is a difference between 'I will eat' and 'I will not eat.'" That is, one who says, "I will not eat," is forbidden to eat even a k'Zayis, whereas one who says, "I will eat," may be obligated to eat the entire loaf. (See CHIDUSHEI REBBI AKIVA to Tosfos, who writes that all of the Rishonim agree with the explanation of the Ritva.) (D. BLOOM)