Positive commandment · Mitzvat Aseh #88 of 613
To eat the remains of the meal offerings
לאכול שיירי מנחות
The verse · Vayikra 6:9
וְהַנּוֹתֶרֶת מִמֶּנָּה יֹאכְלוּ אַהֲרֹן וּבָנָיו מַצּוֹת תֵּאָכֵל בְּמָקוֹם קָדֹשׁ בַּחֲצַר אֹהֶל־מוֹעֵד יֹאכְלוּהָ
“And the remainder of it shall Aharon and his sons eat: with unleavened bread shall it be eaten in the holy place; in the court of the Tent of Meeting they shall eat it.”
The Rambam’s words
To eat the remains of the meal offerings, as [Leviticus 6:9] states: "Aaron and his sons will eat the remainder of it."
לאכול שיירי מנחות, שנאמר: "והנותרת ממנה, יאכלו אהרון ובניו" (ויקרא ו,ט).
Why · Sefer HaChinuch #134
Eating the remainders of the meal-offering
“It is from the roots of the commandment [that] the fundamental principle for us is that all of the acts of the sacrifices are to prepare our thoughts and our intentions for the good, to submerge the spirit of desire within us and to enlarge and strengthen the intellectual spirit towards the commandments.”
Who & when
“And it is practiced at the time of the [Temple] by the males of the priesthood, as it is stated (Leviticus 6:11), “Every male of the Children of Aharon shall eat it.””
Where in the Mishneh Torah
Hilchot Sacrificial Procedure הלכות מעשה הקרבנות