The Torah commands in Parashat Emor (Vayikra 22:22), “Ve’isheh Lo Titenu Me’hem Al Ha’mizbe’ah L’Hashem” – that it is forbidden to place on the altar blemished animal sacrifices. This refers to the “Emurin” – the fats and other parts of the animal sacrifice which are normally placed on the altar. Animals with a physical blemish are disqualified for use as sacrifices, and in this verse the Torah forbids placing the “Emurin” of such animal sacrifices on the altar. Separate commands, as we have seen, forbid consecrating an animal with a physical blemish, slaughtering such an animal, and sprinkling its blood on the altar.
Of course, this prohibition applies only when the Bet Ha’mikdash stands, when there is an altar upon which sacrifices are placed.
The reason for this command, as explained in regard to previous Misvot, is that the Torah wants to ensure that we look to the Bet Ha’mikdash and the sacrifices with reverence and esteem. Offering blemished animals as sacrifices would lower its esteem in the people’s eyes, and so the Torah forbade offering such animals as sacrifices.