Just as we are about to arrive at the apex of the Exodus drama—the final plague and the actual departure from Egypt—the Torah makes a sudden shift in genre.  Chapter 12 opens with, “This month will be for you the first of months,” the marking of the new moon, the first mitzvah given to Israel—and with that, the Jewish legal tradition officially begins.  Having established the calendar, the Torah immediately begins detailing the rituals for what will become the first of its yearly observances: Pesah.  At the center of those rituals are two related mitzvot (eating matzah and not eating hameitz) that together will serve as keys to understanding the role of the mitzvot  in the life of the new people of Israel.