Bechorot 32: The Meat Market

Perek V begins with a new Misha that teaches us that when a sacrificial animal has been redeemed and sold to be eaten, it is sold, slaughtered and weighed in the itliz, meat market.  It is weighed by the litre like other meat.  In contrast, a bechor, firstborn, or ma'aser, tithed animal, that develops a mum, blemish, stops it from being sacrificed.  These animals must be slaughtered at home and cannot be weighed or sold in the meat market.

Tosafot argue that this last restriction is biblical.  The Ramban says that it is rabbinical.  He argues that cannot treat it like other meat and gain additional profit from it in the market.