One of the mitzvot which God issued to Benei Yisrael after the Exodus to commemorate the plague of the firstborn brought upon the Egyptians is peter chamor – the obligation to either redeem or kill a firstborn donkey. The Torah (13:13) writes that a firstborn donkey must be redeemed by giving a sheep to a kohen in its place, and if one does not give the sheep, then he must kill the donkey.
The nature of arifa – the requirement to kill the donkey if it is not redeemed – is subject to a debate between the Rambam and the Ra’avad. The Rambam, in his Sefer Ha-mitzvot (asei 81-82), and in Hilkhot Bikkurim (12:1) counts the obligation of peter chamor as two separate mitzvot in his listing of the Torah’s commands. He lists one command to redeem the donkey with a sheep, and then a second to kill the donkey if one chooses not to redeem it. The Ra’avad disputes the Rambam’s classification, claiming that arifa is not a mitzva, but rather a penalty. As the Gemara comments in Masekhet Bekhorot (10b), the Torah penalizes one who refuses to give a kohen a sheep for the redemption of his firstborn donkey, by forcing him to kill the donkey. Accordingly, the Ra’avad argues, arifa is not a mitzva which one fulfills, but rather a punitive measure against one who refuses to fulfill the mitzva of redeeming his firstborn donkey. The Minchat Chinukh (23) cites the Maharit Algazi as observing that the Mekhilta appears to present two different views on this issue, as to whether arifa constitutes a mitzva or a penalty. The Rambam, apparently, chose to follow the view which considers arifa a mitzva, one of two perfectly valid options, and not as a penalty, whereas the Ra’avad followed the view cited in the Gemara, which sees arifa as a punitive measure.
The Minchat Chinukh, however, suggests that these two perspectives are not mutually exclusive. He notes that the Sefer Ha-chinukh cites the Gemara’s comment that arifa serves to penalize the individual for denying the kohen a sheep, even though the Sefer Ha-chinukh – following the Rambam, as always – counts arifa as one of the 613 mitzvot. Clearly, then, the Sefer Ha-chinukh saw no contradiction at all between regarding arifa as a mitzva and also as a penalty. The Minchat Chinukh explains that even if the reason underlying arifa is to penalize the donkey’s owner, it may nevertheless be counted as a mitzva. After all, one who prefers not to relinquish a sheep is bound by Torah law to kill his donkey, and thus killing the donkey may be viewed as a mitzva, even if its purpose is to penalize the owner. The Minchat Chinukh draws a comparison to chalitza – the special ritual performed by a childless widow and the deceased’s brother if the brother refuses to marry the widow. Chalitza is counted as one of the Torah’s 613 mitzvot (Sefer Ha-mitzvot, asei 217), yet the Behag (cited in the Beit Shemuel commentary to Even Ha-ezer 169:82) describes chalitza as a form of punishment against the brother-in-law for his refusal to marry the widow. This demonstrates that at least in the Rambam’s view, even commands which must be fulfilled due to one’s refusal to do what he should can be counted among the 613 mitzvot. (It is likely that the Ra’avad disputed this very point, as to whether requirements imposed as punitive measures should be counted as Biblical commands.)
Intuitively, we might assume that the practical halakhic difference between these two views relates to the recitation of a berakha before performing the arifa. If, as the Rambam maintains, killing the donkey when one chooses not to give a sheep to the kohen fulfills a mitzva, then it should, seemingly, be preceded by the recitation of a berakha, as are other mitzva acts. The Ra’avad, by contrast, who does not view arifa as a mitzva, would certainly not require the recitation of a berakha before the arifa.
The Minchat Chinukh, however, asserts that even the Rambam would not require a berakha over arifa, since a berakha is not recited over the performance of a mitzva which is the less preferred option. Returning to his analogy to chalitza, the Minchat Chinukh observes that the Tur (E.H. 166) cites the Ba’al Ha-ittur as ruling that the brother-in-law recites a special berakha before marrying the widow, as he fulfills the mitzva of yibum, yet the Tur makes no mention of a berakha over chalitza. The reason, seemingly, is because it is inappropriate to recite a berakha over a mitzva that ideally should not be observed, and was necessitated by a decision not to choose the preferred option. By the same token, the Minchat Chinukh writes, it stands to reason that no berakha should be recited over arifa. Indeed, the Minchat Chinukh notes that the Shulchan Arukh (Y.D. 321:6) mentions a berakha to be recited when redeeming a firstborn donkey with a sheep, but makes no mention of a berakha in discussing arifa, implying that no berakha is recited if one chooses the less preferred option of killing the donkey.