Bechorot 13: On the Option of Decapitation of the Donkey

Today's Misha teaches us that if someone prefers to not exchange his firstborn donkey with a lamb, the donkey is redeemed and decapitated (Shemot 13:13, 34:20).  It is said that mitzvah ha podia kodemet lemitzva arid, the commandment to redeem to redeem [the donkey] is preferred over the mitzvah to decapitate.

Does this mean that decapitation is also a mitzvah in this context?  This is argued rigorously rabbis including the Rambam and the Ra’avad, where mitzvah arifa, the mitzvah of decapitation, is not literal instruction but used to question mitzvah pediya, the mitzvah to redeem.

The rabbis debate about how the Torah could offer a hypothetical option.  One example might be offering yibum, leverage marriage where a childless widow is offered to her widower's husband for marriage, over chalitza, a ritual that frees the widow to marry whomever she'd like.  Both are certainly competing mitzvot, though even today we learn that chalitza is preferred by the rabbis.

Steinsaltz reminds us that the kabbalistic teaching by Radbaz is that decapitation of the donkey should not be read as damaging the animal.  Instead, it should be understood as transporting the animal to a higher level of existence.