Separation by lamb blood
החדש הזה לכם ראש חדשים ראשון הוא לכם לחדשי השנה: דברו וגו’ ויקחו להם איש שה לבית-אבת שה לבית: ואם-ימעט הבית מהית משה ולקח הוא ושכנו הקרב אל-ביתו וגו’ ולקחו מן-הדם ונתנו על-שתי המזוזת ועל-המשקוף על הבתים אשר-יאכלו אתו בהם: והיה הדם לכם לאת על הבתים אשר אתם שם וגו’ ואתם לא תצאו איש מפתח-ביתו עד-בקר: ועבר יקוק לנגף את-מצרים וראה את-הדם על-המשקוף וגו’ ולא יתן המשחית לבא אל-בתיכם לנגף
This month will be for you the beginning of the months; for you it is the first for the months of the year. Tell [the Jewish people that]…they will take for them, each man, a lamb for the fathers’ homes, a lamb for each household. If the lamb will not suffice for the household, they and the neighbor close to their house will take…Take from the blood and place it on the two doorposts, and the lintel of the house that you will eat [the offering] in. The blood will be for you a sign on your houses that you will be in…and you shall not leave, each person, from the door of their house, until morning. Hashem will pass by to afflict the Egyptians, and will see the blood on the lintel…and He will not let the Destroyer come to your houses to afflict
Before the plague of the death of the firstborn, Moshe instructed the Jews with several mitzvos. He started by informing them about the Jewish calendar, in which Nissan is the first of the months. This included details of the mitzvah to sanctify the New Moon, establishing the months accordingly. Subsequently, he informed them of the mitzvah of the Pesach offering. This included instructions on selecting a lamb for each household, taking its blood and putting it on the doorposts, and staying indoors until morning. How are we to understand the juxtaposition of these two mitzvos? As well, upon careful examination, we’ll observe that the first mitzvah given to the Jewish people as a whole is the mitzvah to sanctify the New Moon. Why was this mitzvah held in such high esteem that it merited to get the position as the first mitzvah? Finally, with regards to the Pesach offering, why is there so much emphasis on the house? It’s repeated and stressed multiple times. What could be the reason?