Midrash for Bekhorot 36:39

(Devarim 15:20) "And if there be in it a blemish": This tells me only of an animal that was born unblemished and became blemished. Whence do I derive (the same for) one that was born blemished! From "every blemish." Whence do we derive (the same for animals that are) scrofulous, warty, scabbied, old, sick, or malodorous? From "every." I might think that they could be slaughtered (and eaten) outside Jerusalem; it is, therefore, written "lame or blind': "lame" and "blind" were in the category (of blemished animals). Why did they leave that category (for special mention)? To make them the basis for a comparison, viz.: Just as "lame" and "blind" are distinct in being external blemishes, which do not heal, so, all (blemishes which render a bechor subject to slaughtering and eating outside Jerusalem) must be of that kind.