Negative commandment · Lo Ta’aseh #97 of 613
Not to inflict a disqualifying physical blemish upon a consecrated animal
שלא ייתן מום בקודשים
The verse · Vayikra 22:21
וְאִישׁ כִּי־יַקְרִיב זֶבַח־שְׁלָמִים לַה׳ לְפַלֵּא־נֶדֶר אוֹ לִנְדָבָה בַּבָּקָר אוֹ בַצֹּאן תָּמִים יִהְיֶה לְרָצוֹן כׇּל־מוּם לֹא יִהְיֶה־בּוֹ
“And whoever offers a sacrifice of peace offerings to the Lord to accomplish his vow, or a freewill offering in oxen or sheep, it shall be perfect to be accepted; no blemish shall be in it.”
The Rambam’s words
Not to inflict a disqualifying physical blemish upon a consecrated animal, as [Leviticus 22:21] states: "It shall not have a blemish." This can be interpreted to mean: Do not inflict a blemish upon it.
שלא ייתן מום בקודשים, שנאמר "מום לא יהיה בו" (ויקרא כב,כא); כלומר, לא תיתן בו מום.
Why · Sefer HaChinuch #287
That we not place a blemish upon consecrated animals
“From the roots of the commandment are what you will see at the end of my words. However, I am afraid of drawing close to the Dwelling of G-d, as I know that “anyone who comes close, who comes close” that has not sufficiently sanctified himself “will not see the House and live.””
Who & when
“And this prohibition 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