Yesterday, we noted the theory advanced by the Tosafot Ha-Rosh (Shabbat 21b) and, far more famously, by the Beit Yosef (O.C. 670), that after the Chashmonaim discovered the small jug of pure oil, they divided it into eight equal portions. Realizing it would take eight days for new pure oil would arrive, they decided to fill the lamps of the menorah with one-eighth the normal amount, rather than using the entire jug to kindle the menorah for one night, and then be left without any oil for the next seven nights. As we discussed, later writers raised the question of why, according to this theory, the Chashmonaim added less oil than was required hoping that it would miraculously sustain the candles throughout the night, seemingly in violation of the famous rule of “ein somekhin al ha-neis” – that we are to conduct ourselves within the constraints of the natural order, and not anticipate God’s miraculous intervention.
One answer is given by Rav Yosef Zecharya Stern of Shavel, in his Zeikher Yehosef (vol. 1, O.C. 120), where he explains this theory on the basis of the famous halakhic principle of chatzi shiur. This principle is discussed by the Gemara in Masekhet Yoma (74a), which states that although one is liable to punishment for eating forbidden food only if he eats a certain quantity, it is nevertheless forbidden to eat any quantity. Most prohibitions involving eating are punishable only if one eats a ke-zayit, but the Gemara establishes that eating even smaller amounts is prohibited. According to the accepted position, that of Rabbi Yohanan, the prohibition of chatzi shiur applies on the level of Torah law, and not merely by force of Rabbinic enactment. Meaning, the Torah itself forbids transgressing its prohibitions in any quantity, even in smaller quantities than those which are needed for the court to punish the violator.
Several Acharonim addressed the question of whether the concept of chatzi shiur applies even in regard to the performance of mitzvot. Many mitzvot require a certain quantity or duration, just as many prohibitions involve certain amounts. If a person is able to perform only “half a mitzva,” does he receive credit for a partial mitzva, or is there no value at all to such an act? The classic example given is the case of a person who has access to only a small amount of matza on the night of Pesach, smaller than the minimum amount one is required to eat to fulfill the mitzva of eating matza on this night. Is it worthwhile for the individual to eat the small amount, in order to fulfill the “chatzi shiur” of the mitzva, or is such an act halakhically meaningless, given that the person does not eat the minimum required quantity?
Rav Stern infers from the Beit Yosef’s theory concerning the Chashmonaim’s kindling of the menorah that indeed, the concept of chatzi shiur is relevant even in regard to the performance of mitzvot. According to the Beit Yosef, he explains, the Chashmonaim did not anticipate the oil’s miraculously sustaining the candles throughout the night, but rather chose to achieve “chatzi shiur” – a partial fulfillment of the mitzva – rather than perform the mitzva fully one night, and then not at all for the next seven nights. This was a calculated halakhic decision, Rav Stern suggests, and not the expectation of a miracle.
Rav Asher Weiss, in his discussion of this subject, questions Rav Stern’s line of reasoning. Even assuming that the notion of chatzi shiur applies to mitzva performance, Rav Weiss writes, it is questionable whether one should compromise a complete fulfilment of a mitzva for the sake of multiple opportunities for partial fulfillment. Rav Weiss contends that even if there was value in kindling the menorah for one-eighth the required duration, it would have been preferable to kindle the menorah normally the first night and fulfill the mitzva in its entirety, and then not light at all the next seven nights. The value of a “chatzi shiur” performance of a mitzva is, without question, far inferior to a complete performance, and thus a complete performance should not be sacrificed even for the sake of multiple opportunities for performing a “chatzi shiur.”
Regardless, Rav Weiss notes that in his view, the concept of chatzi shiur is limited to the specific context in which it is discussed – the violation of prohibitions. The Gemara infers the principle of chatzi shiur from a nuance in a verse in the Torah (“kol cheilev” – Vayikra 7:23) referring to the consumption of prohibited foods. As such, this rule cannot be applied beyond this context, and deemed relevant even with regard to the performance of mitzvot. (However, the Gemara also explains the rule of chatzi shiur as based upon the rationale of “chazi le-itzterufei” – that since a partial quantity can potentially combine with another partial quantity to complete the required amount, even partial amounts are deemed significant. One could argue that if this is the basis of the principle of chatzi shiur, then it is relevant even to mitzvot, as for all purposes we regard partial amounts as halakhically significant.)