The Rambam, in the beginning of Hilkhot Shekalim (1:1), writes that even an “ani ha-mitparneis min ha-tzedaka” – a pauper who is supported by charity – is required to give a half-shekel each year towards the Beit Ha-mikdash, in fulfillment of the machatzit ha-shekel obligation. Despite this individual’s unfortunate state of poverty, the Rambam writes, he is required to borrow money or even sell his clothing in order to pay a half-shekel.
Rav Chaim Kanievsky, in his work Shekel Ha-kodesh (1:1, in the Bei’ur Halakha section), addresses the question as to why this should be the case. The Talmud Yerushalmi (Pei’a 1:1) famously writes that a person who does not have money with which to perform a mitzvat asei (affirmative command), such as if he cannot afford a pair of tefillin, is exempt from that obligation. Moreover, the Rama (O.C. 656:1) writes that one does not have to spend more than 20 percent of his assets for the sake of the fulfillment of a mitzvat asei. The well-known exceptions to this rule are the obligation of Chanukah candles and the obligation of four cups of wine on the night of Pesach, which must be fulfilled even if this requires begging, borrowing, or selling one’s clothing (O.C. 472:12, 671:1) – an extraordinary provision which is commonly understood as reflecting the importance of pirsumei nisa (publicizing the miracle celebrated through these mitzvot). The Rambam makes an additional exception for the mitzva of Shabbat candle lighting (Hilkhot Shabbat 5:1), which has been explained based on the halakha which affords precedence to Shabbat candles over Chanukah candles due to the singular importance of shalom bayit (serenity in the home – Shulchan Arukh O.C. 678:1). If Halakha requires a pauper to sell his belongings or beg for the sake of lighting Chanukah candles, the Rambam apparently reasoned, then certainly he should do so for the sake of Shabbat candles, which are deemed more important than Chanukah candles.
In any event, the basic rule is that a person does not have to beg or sell his clothing to fulfill the Torah’s affirmative commands, except in these rare instances. The question thus arises as to why the Rambam considered the machatzit ha-shekel obligation one of the exceptional mitzvot that require even the destitute to do anything they can to be able to fulfill this requirement.
Several writers, including the Sefer Ha-chinukh (105), cite as the source of this law the Torah’s command in Parashat Ki-Tisa (30:15), “The wealthy one shall not add onto, and the impoverished one shall not diminish from, the half-shekel [amount]…” The Torah here explicitly commands that even a pauper must pay the machatzit ha-shekel, and thus this verse might perhaps be the source requiring even the destitute to do what they can to fulfill this obligation. However, Rav Kanievsky questions this conclusion, noting that the Torah may not necessarily be speaking of somebody who is so poor that he must sell his clothing or beg in order to obtain a half-shekel. Quite possibly, the Torah establishes that one who has only less than a half-shekel should not pay anything, rather than pay an amount less than a half-shekel – not that he must resort to extreme means of obtaining money for this mitzva.
Rav Kanievsky notes that some writers suggested drawing proof to the Rambam’s ruling from the case addressed in the Mishna (Shekalim 1:7) of somebody who pays the machatzit ha-shekel on a pauper’s behalf, who is absolved of the requirement to add a “kalbon” (the money changer’s fee for exchanging a whole shekel for two half-shekels). The fact that the Mishna envisions such a scenario would appear to indicate that even the poor were required to participate in the machatzit ha-shekel payment. Clearly, however, as Rav Kanievsky writes, the fact that some might volunteer to enable an impoverished friend to fulfill this mitzva does not mean that the impoverished friend is required to beg for donations for this purpose.
Rav Kanievsky suggests that the Rambam perhaps reached this conclusion on the basis of the fact that the revenue from the machatzit ha-shekel went towards the public sacrifices, which were offered on behalf of the entire nation. The Gemara in Masekhet Zevachim (4a) states that whereas a private sacrifice is disqualified if the kohen tending to the sacrifice had in mind the wrong person (and not the person who brought the offering), no such law applies to the public sacrifices. These sacrifices are brought on behalf of the entire nation, and thus there is no scenario where the officiating kohen could have the wrong person in mind – for all members of the nation are the “owners” of the public sacrifices. As such, since these sacrifices were to represent all members of Am Yisrael, it follows that all members needed to participate in the machatzit ha-shekel donation, even if this entailed resorting to extreme measures such as selling one’s clothing or begging for charitable donations.