Parsha Mitzvot: Tzav: Mitzvah 141 – Concept 365
“It shall not be baked leavened, I have presented it as their share from My fire-offerings; it is most holy, like the sin-offering and like the guilt-offering (Vayikra 6:10).” We may not bake a meal-offering as leavened bread (Rambam, Hilchot Ma’aseh ha-Korbanot – The Laws of the Sacrificial Procedure).
As the Kohanim prepare the offerings on the Altar they are acting out the role of the Angel Michael, who is purifying souls on the Altar in Heaven. Their parallel Service on the Altar purifies the souls of those bringing the offering, and the focus is on the simplest essence of the soul. Therefore, no leaven, or expansion, is permissible. (Ashel Avraham)