Menachot 101: Redeeming Sacrifices that become Ritually Impure, Halacha that Suits Our Needs

Today's daf begins our twelfth perek.  It teaches that once an animal is offered as a sacrifice it cannot be redeemed.  Further, if the animal developed a blemish, it could be redeemed and another animal would be purchased to replace it.

The Mishna states that:

• meal offerings and libations can be redeemed if they were not placed in a special vessel
• if they were placed in that vessel, they can no longer be redeemed 
• fowl or wood used with frankincense that became ritually impure cannot be used nor redeemed
• those fowl/wood must be destroyed

The Gemara notes that restrictions on redeeming wood, frankincense and vessels is rabbinic.  Biblically they can be redeemed even if they were not ritually impure and thus usable.  They could not be redeemed because they are rare and there might not be enough of them for Temple services.  The rabbis teach that wood is common, but not wood without worms.  We learn that the Meiri teaches that wood with worms cannot be used on the altar because:

• only things edible for Jews can be burned on the altar
• worms are disgusting and thus wormy wood would disgrace the altar

It is notable that the rabbis recognize in two different points that halacha might have been created for the benefit of people, not because it was a Torah-based instruction.