1) LIABILITY FOR A SMALL AMOUNT
QUESTION: In the Mishnah (19b), Rebbi Akiva states that when a person makes an oath that "I will not eat" and then he eats even the smallest amount, he violates his Shevu'ah. The Chachamim disagree and maintain that there is no case in the Torah in which a person who eats a small amount of something (less than the amount which makes him liable, such as a k'Zayis) is liable for transgressing a Torah law.
The Gemara (21b) questions this argument of the Chachamim. A person who eats an ant of the smallest possible size is fully liable for transgressing the prohibitions against eating bugs. Clearly, the Torah makes one fully liable for eating a small amount of something that is prohibited. The Gemara answers that when one eats an ant he is liable because the ant is a "Biryah," a complete creature, and as such it is significant even without having a minimum size.
The Gemara asks another, similar question. The law is that a person is liable for benefiting from even a small amount of Hekdesh. (RASHI (DH v'Harei) explains that as long as the value of Hekdesh is a Perutah, one is fully liable for eating it even he eats less than a k'Zayis.) The Gemara answers that Hekdesh still has a minimum amount -- the value of a Perutah. Therefore, one is not considered to be liable for eating the smallest amount, even though it is less than a k'Zayis.
Rava (22a) says that Rebbi Akiva and the Chachamim disagree about the law in the case of a person who swears, "I will not eat," but he does not say how much he will not eat. They agree that one who swears, "I will not eat anything," is liable for eating the smallest amount, in the same way that one is liable for eating a Biryah.
In the Gemara later, Rav Papa says that the dispute between Rebbi Akiva and the Chachamim applies only in the case of a Shevu'ah. They agree in the case of a Neder; when a person forbids an item to himself with the term "Konam" (he says, "This loaf of bread is Konam on me"), he is liable for eating even a small amount. This is because making a Neder with the word "Konam" (without mentioning "eating" at all) is tantamount to explicitly stating "anything," in which case one is liable for even a small amount, as Rava states.
TOSFOS (DH Aval) questions Rav Papa's assertion that everyone agrees that using the word "Konam" makes one liable for a small amount. The Mishnah in Nedarim (10a) states that the word "Konam" is an alternative way of saying "Korban"; when a person says that a loaf of bread is "Konam" on him, it is equivalent to saying that the bread is forbidden to him the same way a Korban is forbidden to him.
If the word "Konam" makes the item forbidden to him like a Korban, how can the laws of Konam be more stringent than the laws of Hekdesh? Since the Gemara states that one is not liable for eating Hekdesh worth less than a Perutah, how can the law of Konam, which itself is derived from Hekdesh, make one liable for eating a small amount? The law of Konam cannot be more stringent than the source from which it is derived, Hekdesh.
ANSWERS:
(a) The TOSFOS HA'ROSH answers that although the law of Konam is derived from Hekdesh, the amount of a prohibition of Konam is not derived from the amount of the prohibition of Hekdesh. Since the person made the bread forbidden to him but did not mention that it was forbidden to eat, his intent must have been to make even the smallest amount forbidden.
The TORAS CHAIM elaborates on this answer. When a person sanctifies an object, his specific intent is to sanctify it for the purposes of the Beis ha'Mikdash. The effect of his words is that the object becomes forbidden to him. Once it is forbidden as Hekdesh, a Gezeiras ha'Kasuv states that he is liable to bring a Korban Me'ilah only if he derives benefit worth more than a Perutah. In contrast, when a person says that a loaf of bread is "Konam" for him, his specific intent is that it should be forbidden to him. Since he did not mention "eating," he is forbidden from eating even a small amount.
(b) The RAMBAN and RASHBA distinguish between the obligation to bring a Korban for accidental transgression of one's vow, and the obligation to receive Malkus for willful transgression of one's vow. Accidental transgression of a vow of Konam must be identical to an accidental transgression of a vow of Hekdesh (as there is no Korban brought for the accidental transgression a Neder). Accordingly, only if one derives benefit worth a Perutah, and the benefit was derived inadvertently, is he obligated to bring a Korban, just as he is obligated to bring a Korban when he derives benefit worth a Perutah, inadvertently, from Hekdesh. Rav Papa, in contrast, refers to one who willfully derives benefit from the object of his Neder, who is punished with Malkus, which is clearly not the same as the law for one who willfully derives benefit from Hekdesh. This is because the prohibition against violating a vow is independent from the prohibition against deriving benefit from Hekdesh. (See REBBI ELIEZER MOSHE HA'LEVI HOROWITZ on Tosfos who also expresses this idea.) (D. BLOOM)

22b----------------------------------------22b

2) IS EATING EARTH CONSIDERED EATING?
QUESTION: Rava rules that one who swears that he will not eat, and then he eats soil, is exempt from a Korban for transgressing this oath. RASHI (DH v'Achal) explains that since soil is inedible, he is considered as though he did not eat anything.
The ROSH (#5) writes that a different text appears in earlier manuscripts of the Gemara. According to those manuscripts, Rava says that one who swears that he will eat, and then he eats soil, has fulfilled his oath.
The RAMBAM (Hilchos Shevu'os 5:5) rules in accordance with both of these texts. This is difficult to understand, because the two versions of Rava's statement are mutually exclusive. The first version maintains that eating earth is not considered eating, while the second version maintains that it is considered eating.
ANSWERS:
(a) The LECHEM MISHNEH explains that the Rambam writes that eating soil is considered eating "because for the person who eats it, it is considered a significant act of eating." This is consistent with the words of the Rosh, who writes that the fact that the person eats soil in order to fulfill his oath to eat proves that he considers it a significant act of eating ("Achshevei" - "he made it important").
In contrast, one who swears that he will not eat and then he eats soil clearly shows that the eating of soil is not considered an act of eating to him. The Lechem Mishnah adds that the Chazakah that a person is not an evildoer supports the assumption that the person in this case does not consider eating soil an act of eating, for it is assumed that he does not want to transgress his oath.
(b) The RAN (9a of the pages of the Rif) similarly differentiates between a person who swears that he will eat and a person who swears that he will not eat. A person who swears that he will not eat has in mind not to eat edible food, since it is unnecessary to swear that he will not eat inedible items, which he would not eat even without an oath.
In contrast, a person who swears that he will eat wants to be able to fulfill his oath in any way possible so that he will not suffer the punishment of making a false oath. Therefore, he has in mind that eating soil also should be considered eating so that he can fulfill his oath even by eating soil.
The CHASAM SOFER suggests that a practical Halachic difference between these two answers exists in a case in which a person swears, "I will not eat tomorrow if I eat today."
According to the Lechem Mishneh's explanation, if the person eats soil today, he shows that eating soil is a significant act of eating to him (since he eats it after making an oath that depends on eating today). Accordingly, he is considered as though he has eaten today, and his oath not to eat tomorrow takes effect.
In contrast, according to the Ran's explanation, a person's primary intention is to avoid punishment for a false oath. Therefore, when he made his oath dependent on "if I eat today," he meant only an ordinary act of eating. This is because he wants to minimize the chances that his oath will take effect tomorrow, lest he violate it and be punished. Consequently, even though he eats soil today, his act is not considered an act of eating. His oath does not take effect and he is permitted to eat tomorrow. (D. BLOOM)

OTHER D.A.F. RESOURCES
ON THIS DAF