The Torah commands in Parashat Emor (Vayikra 22:21), “Kol Mum Lo Yiheyeh Bo” – literally, “…no blemish shall be in it [an animal sacrifice].” The Sages understood this verse to mean not that an animal sacrifice should not have a blemish, but rather that one may not make a blemish in an animal consecrated as a sacrifice, a prohibition known as “Matil Mum Be’kodashim.”
The reason behind this prohibition, the Sefer Ha’hinuch explains, is that making a blemish in an animal sacrifice would denigrate the service in the Bet Ha’mikdash, and lower its esteem in the people’s eyes. The Torah places great emphasis on ensuring that the people look upon the Bet Ha’mikdash and its service with great honor and respect, and therefore it forbids degrading the sacrifices by making a blemish in a consecrated animal.
This prohibition applies both to consecrated animals and to a “Temura” – an animal onto which one transferred the sanctity of a consecrated animal. The Torah forbids declaring the transfer of a consecrated animal’s sanctity onto a different animal, but if one did make such a declaration, both animals are deemed sacred. One would then violate the prohibition of “Matil Mum Be’kodashim” by making a blemish in either animal.
One who makes a blemish in a consecrated animal, or its Temura, has transgressed this prohibition and is liable to Malkut. The exception to this rule is the case of the Temura of a Bechor (firstborn animal) or of Ma’aser Behema (the tithe of a herd, which are offered as sacrifices). Since the Temura of a Bechor or Ma’aser Behema is not eligible to be brought as a sacrifice, one is not liable to Malkut for making a blemish in such an animal.
This prohibition applies at all times, even nowadays, in the absence of the Bet Ha’mikdash. It is possible to consecrate an animal as a sacrifice even nowadays, and if an animal was consecrated, one who makes a blemish in the animal violates this prohibition.
Of course, this prohibition is binding upon both males and females.