This being the Shabbat that falls on or before the first of Nissan, we also read the section of Hachodesh (Exodus 12:1–20), which relates G‑d’s words to Moses in Egypt two weeks before the Exodus, instructing us to set the Jewish calendar by the monthly new moon, and to regard Nissan as the “head of months.” G‑d also instructs to bring the Passover offering, to eat it with matzah and bitter herbs, and to abstain from leaven for seven days.