Breaking the Neck of the Unredeemed Firstling Donkey

"And if you will not redeem it, then you shall break its neck" (Exodus 13:13). From here they said: if a man does not redeem the firstling donkey, he must break its neck, for since he has destroyed the property of the priest [by withholding the lamb owed as redemption], let his own property be destroyed as well. And from where do we learn that the carcass is forbidden in benefit [that one may derive no use or profit from it]? "Breaking of the neck" is stated here, and "breaking of the neck" is stated elsewhere [regarding the heifer whose neck is broken in the case of an unsolved killing, Deuteronomy 21]. Just as the breaking of the neck stated there renders the animal forbidden in benefit, so too the breaking of the neck stated here renders the animal forbidden in benefit.