Osek B’Mitzvah Patur Min HaMitzvah

On the surface, the rule of Osek B’Mitzvah Patur Min HaMitzvah,
that involvement in one mitzvah exempts one from tending to another that presents itself seems to be a simple aspect of reality: it’s impossible to do two things at once. Thus, G-d recognizes human limitations and does not hold one responsible for not doing that which it is impossible to do. However, if that were indeed the situation, a special halakhah, derived from verses, would be unnecessary. Thus, another aspect must be involved. Rishonim differ as to what that aspect is.

The Ritva (Sukkah 25a) suggests that the message of this halakhah is that one is not only not obligated but is not permitted to abandon the first mitzvah to take up a second mitzvah he deems more important. The Rambam makes a similar statement concerning the mishnaic exhortation (Avot 2:1) to be as careful with a “light mitzvah” as with a “weighty mitzvah”. As we are ill-equipped to assess the relative value of mitzvot, it is inappropriate to negelect a current obligation in favor of one that comes along afterward, however worthy (see also Maharach Ohr Zarua, 183.)

The assumption of the Ritva is that the relevant scenario is one where it is impossible to accomplish both mitzvot; if it were possible, there would be no exemption. This position is shared by Tosafot (Bava Metzia 56b). However, other rishonim disagree. The Ran (Sukkah 11a bdapei haRif) is of the opinion that the exemption applies even if it is possible to do the other mitzvah and still finish the first. The Ohr Zarua (Hil.Sukkah, 229) concurs, noting that otherwise, there would be no need for a special halakhah. In the Ran’s assessment, this rule teaches that the Torah does not obligate one to trouble himself to perform a mitzvah if he is already involved in one. He notes, though, that if no trouble (tirchah) is involved, it is laudable to do both mitzvot. The Rama (Orach Chaim 38:8) rules that one is exempt from a second mitzvah if tirchah is called for, but if not, one must do both. The Responsa Chavalim B’N’imim (II, 3) builds on the Ran’s position by noting that one would be exempt even if he could perform the second mitzvah through a shaliach; if he is exempt, then the shaliach is also.

Thus, two schools of thought appear to exist in explaining the novelty of Osek B’Mitzvah Patur Min HaMitzvah. Acoording to the Ritva, it is in the scope of the exemption – which is not merely a dispensation but factors as a prohibition. According to the Ran, the focus is one the conditions creating the exemption – not only when it is impossible to perform the second mitzvah, but even when it is merely burdensome.

These possibilities would be relevant to the question of how absolutely to aapply the exemption: is the second mitzvah complety nullified, vis-à-vis the occupied individual, or is the obligation still active, although the indivual is excused for not participating.

An issue affected by that question would be a situation in which one is exempt from a second mitzvah and yet performs it nonetheless. Would that second obligation be considered discharged? The standard rule is a mitzvah performed during a period of exemption is not considered fulfilled. This is the case when one performs a mitzvah while temporarily mentally incapacitated (Rosh HaShanah 28a; Rambam, Hil. Chametz U’Matzah 6:3: Shulchan Arukh. O.C 475:5.) The Ritva’s position seems to assign to the second mitzvah a status of completely inapplicable. (However, note Resp. L’Horot Natan, VIII, 30, who takes the opposite understanding.) Conversely, the Responsa Rama MiPanu (#102) states that one who is preoccupied with a mitzvah and yet exerts himself to accomplish another, “grabs two”, in other words, fulfills both commandments. (See Sha’ar HaTziyyun, 475:39, who is unsure whether it would be permissible to recite a b’rakhah on the second mitzvah. See also Zevachim 19a, and Sha’agat Aryeh, 37).

Other ramifications of this question would include whether one choosing to fulfill the second commandment can discharge the obligation of another individual who listens to him (see Maharach Ohr Zarua 183) as well as the issue of whether one who is exempt from a mitzvah that can be made up later (e.g., prayer) is obligated to do so (a topic of dispute between the Drishah and the Taz (Y.D. 341:5).

The issue mentioned above as to the circumstances necessary for exemption has also provoked much discussion, including such questions as: a possible mitzvah exempting from a mitzvah that is definite (see Imrei Binah, O.C. 13); a nonobligatory commandment’s ability to exempt (see Netivot HaMishpat, 291:3, and Resp. Har Tzvi, O.C. 104); the role of a hekhsher mitzvah (see Birkat Avraham, Ketubot 6b); a mitzvah d’rabbanan exempting from a mitzvah d’orayta (see Resp. Chavalim B’N’imim, ibid.); and whether the exemption applies if the second mitzvah is an interpersonal mitzvah.