1) BURNING CHAMETZ ON PESACH ACCORDING TO REBBI AKIVA
QUESTION: Rebbi Akiva proves that the obligation to destroy Chametz applies before Pesach begins. The Torah commands us to burn the Chametz, and kindling a fire is forbidden on Yom Tov as an Av Melachah. It must be that the requirement to burn the Chametz takes effect before Pesach begins.
RABEINU CHANANEL asks that even if kindling a fire would not be an Av Melachah (for which one is Chayav Kares) but only an Isur Lav (a normal prohibition for which one is Chayav Malkus), one would still be forbidden to transgress the Torah's prohibition against kindling a fire in order to burn the Chametz on Yom Tov. Why, then, does Rebbi Akiva say that Bi'ur Chametz must be done before Pesach because kindling a fire is an Av Melachah which may not be done on Yom Tov? Even if kindling a fire is an Isur Lav, Bi'ur Chametz still must be done before Pesach, because one is not permitted to transgress an Isur Lav for the sake of Bi'ur Chametz.
Rabeinu Chananel answers that if kindling a fire would be an Isur Lav, then it would be permissible to kindle a fire on Yom Tov in order to burn the Chametz. This is because the requirement to burn Chametz is a Mitzvas Aseh, and a Mitzvas Aseh overrides an Isur Lav ("Aseh Docheh Lo Ta'aseh"). Rebbi Akiva's proof that Bi'ur Chametz must be done before Pesach is from the fact that kindling a fire on Yom Tov is an Av Melachah. Kindling a fire is prohibited by the Mitzvas Aseh of Shevisas Yom Tov and not merely by the Lo Ta'aseh, and therefore a Mitzvas Aseh cannot override the prohibition.
This answer is problematic. Even if kindling a fire on Yom Tov would be an Isur Lav, why would the principle of "Aseh Docheh Lo Ta'aseh" apply in this case? The Lav (lighting the fire) is transgressed long before the Mitzvas Aseh (destroying the Chametz) is fulfilled. One transgresses the prohibition against kindling a fire on Yom Tov when he kindles a fire of any size (Rambam, Hilchos Yom Tov 4:1), while he fulfills the Mitzvah of "Tashbisu" only when all of his Chametz has been destroyed. Consequently, he does not transgress the Lav at the same time that he performs the Aseh. In such a case, the principle of "Aseh Docheh Lo Ta'aseh" does not apply (Beitzah 8b).
ANSWER: HA'GA'ON RAV MEIR SHAPIRO zt'l (the Lubliner Rav, Rosh Yeshiva of Yeshivas Chochmei Lublin, and founder of the study of Dafyomi) answers that until all of the Chametz is burned, one is not Chayav for lighting a fire, even though he has not yet fulfilled the Mitzvah of Bi'ur Chametz. One is not Chayav for a Melachah which accomplishes no productive purpose ("Mekalkel"), and thus when he lit the fire for the sake of burning the Chametz, he accomplished no productive purpose. Only when the fire completely destroys the Chametz does the fire accomplish its purpose (see Tosfos to Shabbos 106a, DH Chutz). Since the fire accomplishes its purpose at the moment that the Mitzvah of Bi'ur Chametz is fulfilled, the Aseh overrides the Lo Ta'aseh.
(Rav Meir Shapiro proves that Rebbi Akiva does not agree with the view of Rebbi Shimon (Shabbos 106a) that one is Chayav for Mekalkel of Mav'ir and Chovel, even though one is not Chayav for an act of Mekalkel of any other Melachah. Since Rebbi Akiva maintains that one is exempt even for an act of Mekalkel of Mav'ir, he emphasizes that Mav'ir on Shabbos is an Av Melachah and is accompanied by an Aseh and Kares (and by an Aseh on Yom Tov) such that the Aseh of "Tashbisu" does not override it.) (OR L'ME'IR Siman 61)
2) DETERMINING WHETHER A "MELACHAH" IS AN "AV" OR A "LAV"
QUESTION: The Gemara derives from the wording of Rebbi Akiva that "Hav'arah l'Chalek Yatzas" -- the Torah specifically mentions the Isur of kindling a flame on Shabbos in order to teach that just as one is Chayav (and is punished with Kares for an intentional transgression, and is required to bring a Korban Chatas for an unintentional transgression) when he performs a single Melachah of Hav'arah, when he performs any one of the 39 Melachos he is also Chayav (and he does not have to perform all 39 Melachos in order to be Chayav). Rebbi Akiva argues with Rebbi Yosi who says that "Hav'arah l'Lav Yatzas" -- the Torah specifically mentions the Isur of kindling because kindling is only a Lav and not a Chiyuv Kares.
How does the Gemara derive from Rebbi Akiva's words that he argues with Rebbi Yosi?
(a) RASHI explains that from the fact that Rebbi Akiva calls Hav'arah an "Av Melachah" and not an "Isur Lav," it is evident that he maintains that it is an Av Melachah for which one is Chayav Kares (or Chatas).
(b) The RIVA, cited by TOSFOS (DH l'Chalek), explains that if Rebbi Akiva was of the opinion that Hav'arah is only a Lav on Shabbos, then on Yom Tov (such as Pesach, the subject of the Gemara here), there would be no prohibition whatsoever to light a fire. The Torah commands us not to do "Melachah" on Yom Tov. What is defined as Melachah? The Riva explains that Melachah is an act for which a person is Chayav Kares on Shabbos for its intentional transgression. An act which is only an Isur Lav on Shabbos is not considered a Melachah, and therefore it would not be forbidden at all on Yom Tov.
An interesting ramification of the argument between Rashi and the Riva involves the Mitzvos of Shevisas Behemah (the requirement to let one's animals rest) and Shevisas Avadim (the requirement to let one's slaves rest) on Yom Tov, and the Isur of "Mechamer" that accompanies those two Mitzvos. The positive requirement to let one's animal rest on Shabbos is only a Mitzvas Aseh, and the prohibition against making one's servant or animal work on Shabbos is a Lo Ta'aseh. There is no Chiyuv Kares involved. On Yom Tov, then, what is the Halachah? May one let his servant or animal work on Yom Tov?
1. The BEIS YOSEF (OC 246) infers from the words of RAV HAI GA'ON that there is no Isur of Shevisas Behemah on Yom Tov. This is also the ruling of the REMA (OC 246:3).
2. However, the Beis Yosef elsewhere (OC 495) questions Rav Hai Ga'on's opinion. Why should Shevisas Behemah differ from any other Melachah and not apply on Yom Tov? Even though the Torah does not specifically prohibit Mechamer on Yom Tov, the Torah also does not specifically prohibit all of the other Melachos on Yom Tov, but they nevertheless apply on Yom Tov. Indeed, the RIF and ROSH in Beitzah (36b) clearly state that Shevisas Behemah and Mechamer do apply on Yom Tov.
This question seems to depend on the argument between Rashi and the Riva. According to Rashi, even an act which is prohibited only because of a Lo Ta'aseh on Shabbos (like Hav'arah) should be forbidden on Yom Tov, even though it is not called an Av Melachah. The ruling of the Rif and Rosh seem to follow the view of Rashi.
In contrast, Rav Hai Ga'on -- who rules that Mechamer does not apply on Yom Tov -- seems to follow the view of the Riva, who says that any act that is forbidden only because of a Lav is not called a Melachah and should not be forbidden on Yom Tov at all. (Even according to the Riva, however, there is an Isur d'Rabanan of Shevisas Behemah on Yom Tov. The MAGEN AVRAHAM (OC 246:3) explains that causing one's animal do work is an Uvda d'Chol, a weekday activity.)
3) HALACHAH: LEGAL RESPONSIBILITY FOR CHAMETZ
OPINIONS: The Gemara teaches that if a Jew accepts responsibility for the Chametz of a Nochri, he is obligated to get rid of it before Pesach. Even though he does not own the Chametz, the fact that he is responsible for it gives him the status of owner. If it remains in his possession during Pesach, he will transgress the prohibitions of Bal Yera'eh and Bal Yimatzei.
What extent of responsibility ("Kabalas Achrayus") for Chametz in one's possession requires that he destroy it before Pesach?
(a) The BEHAG (cited by the ROSH) says that even the degree of responsibility of a Shomer Chinam obligates the person to destroy the Chametz. A Shomer Chinam is not responsible for anything that happens to the Chametz (such as theft and loss beyond his control), except for damage or loss due to his own negligence ("Peshi'ah"). Nevertheless, his degree of responsibility is enough to make the Chametz considered to be in his possession, and thus he must get it out of his possession before Pesach.
(b) The RI (cited by the ROSH; see also TOSFOS to Bava Metzia 82b and Shevuos 44a) and the RAMBAM (Hilchos Chametz u'Matzah 4:3) rule that one is not obligated to get rid of a Nochri's Chametz entrusted to him unless he is responsible for its theft and loss as well. This is inferred from the Gemara here which quotes Rava who told the people of Mechuza that they must get rid of the Chametz in their domains because "if it is stolen or lost, you will be responsible for it." Accordingly, a Shomer Chinam is not obligated to destroy the Chametz entrusted to him.
(c) The RID (in the SHILTEI GIBORIM) and TOSFOS in Shevuos (44a) and Bava Metzia (82b) infer from RASHI that the obligation to destroy Chametz applies only when one accepts upon himself to be responsible even for any uncontrollable loss or damage that occurs ("Ones").
(d) RASHI here (6a, DH l'Olam a'Seifa) implies that only when one is able to use the Chametz does he have sufficient liability to make him obligated to get rid of the Chametz. If he cannot use the Chametz, then he is not obligated to get rid of it.
HALACHAH: The SHULCHAN ARUCH (OC 440:1) writes that l'Chatchilah, one should follow the stringent ruling of the Behag and get rid of Chametz entrusted to him even if he is only a Shomer Chinam. However, b'Di'eved, if he cannot return the Chametz to the Nochri before Pesach, he does not have to destroy it. In such a case he may rely on the second opinion; since he did not accept liability for theft and loss, he is not considered the owner of the Chametz and he does not have to destroy it.