The 82nd mitzvah is that we are commanded to break the neck1 of our first-born donkey if we don't want to redeem it.
The source of this commandment is G‑d's statement,2 "[The first-born of a donkey must be redeemed with a sheep,] and if it is not redeemed, you must break its neck."
The details of this mitzvah are explained in tractate Bechoros.3
It is possible for one to ask: "Why are redemption and breaking its neck counted as two separate mitzvos instead of just one mitzvah? The [option of] breaking its neck would then be included in this mitzvah, as explained in the Seventh Introductory Principle.4
This would indeed be the case if not for the fact that we find a statement of the Sages5 which indicates otherwise: "The mitzvah of redemption is preferable to the mitzvah of breaking its neck; and the mitzvah of yibum is preferable to the mitzvah of chalitzah."6 The explanation of this statement is as follows: one may perform either yibum or chalitzah on a yevamah — yibum being a mitzvah, as is mentioned, and chalitzah counting as a separate mitzvah. So too, our Sages said,7 a first-born donkey may either be redeemed or have its neck broken — and each counts as a separate mitzvah.
