Negative commandment · Lo Ta’aseh #139 of 613
Not to partake of the meat of the sin offerings [whose blood is sprinkled] within [the Temple sanctuary]
שלא לאכול בשר חטאות הנעשות בפנים
The verse · Vayikra 6:23
וְכׇל־חַטָּאת אֲשֶׁר יוּבָא מִדָּמָהּ אֶל־אֹהֶל מוֹעֵד לְכַפֵּר בַּקֹּדֶשׁ לֹא תֵאָכֵל בָּאֵשׁ תִּשָּׂרֵף
“And no sin offering, of which any of the blood is brought into the Tent of Meeting to be sprinkled in the holy place, shall be eaten: it shall be burnt in the fire.”
The Rambam’s words
Not to partake of the meat of the sin offerings [whose blood is sprinkled] within [the Temple sanctuary], as [Leviticus 6:23] states: "Any sin offering whose blood has been brought...."
שלא לאכול בשר חטאות הנעשות בפנים, שנאמר "וכל חטאת אשר יובא מדמה" (ויקרא ו,כג).
Who & when
“And this prohibition of eating the inner sin-offering is practiced by the priests.”
Where in the Mishneh Torah
Hilchot Sacrificial Procedure הלכות מעשה הקרבנות