1) EXEMPTING ONESELF FROM LIABILITY IN A CASE OF A "PESHI'AH"
QUESTION: The Mishnah states that when a Shomer Chinam is given an object to watch, he may stipulate that in the event of a loss, theft, or Ones, he will be exempt from paying and will not be obligated to make a Shevu'ah. Likewise, a Sho'el -- who normally is obligated to pay in cases of loss, theft, or Ones -- may stipulate that he will be exempt from such liability.
The Rishonim ask why the Mishnah does not also say that a Shomer Chinam may stipulate that he will be exempt from having to pay in the event of Peshi'ah. Just as a Sho'el may make a stipulation to exempt himself from the usual obligation of a Sho'el to pay, a Shomer Chinam should also be able to stipulate that he will be exempt in the event of Peshi'ah.
(a) RABEINU YEHONASAN (cited by the Shitah Mekubetzes) answers that no person of sound mind would attempt to make a stipulation to exempt himself from paying if he is Poshe'a, because such a person would not be called a "Shomer" at all but a "Mazik"! A person who deposits an item with a Shomer does so with the understanding that the Shomer will guard it, not damage it. Hence, every Shomer accepts upon himself some degree of responsibility to guard the object. The only flexibility that exists with regard to exempting himself from a Shevu'ah is in a case of loss, theft, or Ones.
(b) The HAGAHOS ASHIRI writes that since the Mishnah does not list this as one of the stipulations that a Shomer may make, it implies that a Shomer Chinam is always obligated to pay in a case of Peshi'ah, even if he stipulated that he would be exempt.
It seems that there is a practical Halachic difference between these two answers. According to the Hagahos Ashiri, even if a Shomer does stipulate that he should be exempt from liability for Peshi'ah, he still is obligated to pay. According to Rabeinu Yehonasan, however, he indeed is exempt from liability. This is also the view of TOSFOS (93b, DH Iy) and the ME'IRI.
(c) RAV SHLOMO EIGER (in Gilyon Maharsha) cites the SHEVUS YAKOV who answers this question as follows. It is obvious that when a Shomer Chinam stipulates that he will be exempt in a case of Peshi'ah, the stipulation is valid and he is exempt from payment. A Shomer who makes such a stipulation effectively removes from himself the basic obligation to guard the object. It is as if he has stipulated that he should be permitted to be negligent with the object, in which case he certainly does not become a Shomer. In each case that the Mishnah mentions, there is a Havah Amina that the stipulation would not be effective because it runs counter to the law written in the Torah and thus constitutes "Masneh Al Mah she'Kasuv ba'Torah." The Mishnah therefore must teach that in each of these cases, a Shomer can deviate from the laws that the Torah established for a Shomer. In contrast, when a Shomer Chinam stipulates that he will not be obligated in a case of Peshi'ah, this is not a case of "Masneh Al Mah she'Kasuv ba'Torah" because he is not attempting to change the Torah's rules for a Shomer. Rather, he is refusing to accept upon himself the obligations of a Shomer. Hence, the Mishnah does not need to mention that case. In the cases that the Mishnah does discuss, the person accepts upon himself the title (and laws) of a Shomer and merely wishes to exempt himself from a Shevu'ah or from a certain form of liability. (I. Alsheich)
2) EXEMPTING ONESELF FROM A "SHEVU'AH" IN A CASE OF "MEISAH MACHMAS MELACHAH"
QUESTION: The Mishnah states that when a Sho'el borrows an object, he may stipulate that he will be exempt from payment in the event of loss, theft, or Ones. Why does the Mishnah not mention that a Sho'el may stipulate that he will be exempt from a Shevu'ah in the event of "Meisah Machmas Melachah" (when the animal dies in the course of normal work)? In such a case, a Sho'el normally is exempt from payment but must make a Shevu'ah.
ANSWER: The DEVAR YAKOV answers that this Mishnah is a continuation of the previous Mishnah (93a). Since the previous Mishnah does not discuss the exemption of a Sho'el in a case of "Meisah Machmas Melachah," the Mishnah here does not mention it either. (I. Alsheich)
3) "MILSA D'ASYA B'KAL VA'CHOMER TARACH V'CHASAV LAH KRA"
QUESTION: The Gemara asks what the source is for the Halachah that a Shomer Sachar is obligated to pay in a case of Aveidah. The Gemara answers that his obligation is derived from the repetition in the verse "Im Ganov Yiganev" (Shemos 22:11). The Gemara then asks that this answer suffices only according to the opinion that the Torah "does not speak in the style of man." That opinion maintains that when the Torah uses a repetitious term such as "Im Ganov Yiganev," the extra word is meant to convey a piece of information. However, another opinion maintains that the Torah does speak in the style of man, and according to that opinion nothing can be inferred from the extra word in the verse. What, then, is the source of the Halachah that a Shomer Sachar is obligated for Aveidah? The Gemara answers that the source is a Kal va'Chomer: if a Shomer Sachar is liable for a stolen object even though Geneivah is more similar to an Ones, he certainly should be obligated to pay for a lost object, since Aveidah is more similar to negligence.
The Gemara explains that according to the first opinion, although there is a Kal va'Chomer the extra word in the verse still teaches that a Shomer Sachar is obligated for Aveidah because "Milsa d'Asya b'Kal va'Chomer, Tarach v'Chasav Lah Kra" -- "the Torah troubles itself to write explicitly that which can be learned from a Kal va'Chomer."
What is the logic behind this principle? If a Halachah is known from a Kal va'Chomer, why would the Torah add extra words to teach it? Moreover, a Kal va'Chomer is the most logical and understood of the thirteen methods that the Chachamim use to extrapolate the Halachah from the verses of the Torah. In fact, a person may use the rules of Kal va'Chomer to derive a Halachah even if he has no tradition to make such a Kal va'Chomer. This is in contrast to a Gezeirah Shavah, for which there must be a tradition from Sinai. Why, then, is it necessary for a verse to repeat something that can be derived from a Kal va'Chomer? Indeed, the Gemara never mentions such a principle with regard to any of the other thirteen methods of Halachic derivation, such as a Gezeirah Shavah, although it would seem to make more sense for the Torah to trouble itself to write a Halachah that can be derived from a Gezeirah Shavah since a Gezeirah Shavah does not have any apparent logic to it.
ANSWER: The BNEI YISSACHAR (Chodesh Adar, Ma'amar 10, cited by YOSEF DA'AS) explains that none of the other thirteen methods are based on human logic. They are purely methods of derivation taught at Sinai. The only exception is a Kal va'Chomer which, in addition to having been taught at Sinai, also has some logical basis. The Torah troubles itself specifically to write a law that can be learned through a Kal va'Chomer, the only type of Halachic derivation with a logical basis, in order to teach that all of the Mitzvos of the Torah are beyond logical understanding and must be fulfilled merely because they are the will of Hash-m.
Perhaps this also explains the principle stated in Shabbos (132a) and Pesachim (81b) that "Ein Danin Kal va'Chomer me'Halachah" -- a Kal va'Chomer cannot be used to derive a second Halachah from a Halachah l'Moshe mi'Sinai. RASHI there explains "that Torah she'Ba'al Peh is not given to be expounded with the thirteen methods." This seems difficult to understand. If a Kal va'Chomer is a logical tool, then why should a Kal va'Chomer not be made from a Halachah l'Moshe mi'Sinai? The answer is, as mentioned above, that if the methods of Halachic derivation had not been taught at Sinai, man would not have been permitted to extrapolate a new Halachah through any method, regardless of how logical it might be. The Chachamim are able to apply the methods of Halachic derivation only because the Torah teaches that they may do so, but the Torah permits this only with regard to laws written explicitly in the Torah. Since that license is not given with regard to Torah she'Ba'al Peh, even a Kal va'Chomer may not be made. This is the reasoning behind the principle, "Ein Danin Kal va'Chomer me'Halachah." (I. Alsheich)