Negative commandment · Lo Ta’aseh #91 of 613
That we not consecrate animals with blemishes for the altar
שלא להקדיש בעלי מומין למזבח
The verse · Vayikra 22:20
כֹּל אֲשֶׁר־בּוֹ מוּם לֹא תַקְרִיבוּ כִּי־לֹא לְרָצוֹן יִהְיֶה לָכֶם
“But whatever has a blemish, that shall you not offer: for it shall not be acceptable for you.”
The Rambam’s words
Not to consecrate animals with disqualifying physical blemishes [as sacrifices to be offered on] the altar, as [Leviticus 22:20] states: "Any [animal] which has a blemish shall not be sacrificed." This prohibition involves [the animal's] consecration.
שלא להקדיש בעלי מומין למזבח, שנאמר "כול אשר בו מום, לא תקריבו" (ויקרא כב,כ); זה הוא איסור הקדשו.
Why · Sefer HaChinuch #285
That we not consecrate animals with blemishes for the altar
“It is from the roots of the commandment to aggrandize the glory of the [Temple] and its beauty. Therefore it is not fitting for someone with a blemish to go there — since it is the place of perfection, it is not appropriate for someone with any lack to stand there.”
Who & when
“And [it] is practiced in every place and at all times by males and females.”
Where in the Mishneh Torah
Hilchot Things Forbidden on the Altar הלכות איסורי המזבח