And the 40th mitzvah is that we are commanded that the High Priest shall bring a meal-offering continually each day, in the morning and the evening. It is called "chavitin1 of the High Priest," as well as "minchas Kohen mashiach" [meal-offering of the anointed Priest].
The source of this commandment is G‑d's statement2 (exalted be He), "This is the offering that Aaron and his descendants must bring to G‑d."
The details of this mitzvah, and when and how it is brought have been explained in the 6th3 and 9th chapter of Menachos,4 and many places in Yoma,5 and Tamid.