Parashat Bo includes the first Mitzvah given to Bnei Yisrael, the Mitzvah of Rosh Chodesh: “HaChodesh HaZeh Lachem Rosh Chodashim Rishon Hu Lachem LeChodshei HaShanah,” “This month is for you the beginning of months, it is for you the first of the months of the year” (Shemot 12:2). In this single Pasuk, the Torah reveals a great deal of hidden meaning about the essence of Rosh Chodesh, and specifically Nissan, the first month of the year.
According to a Pshat interpretation of the Pasuk, the Mitzvah of Rosh Chodesh seems not to be a responsibility of Bnei Yisrael at all! The Pasuk says that Nissan is the first month – this has nothing to do with the actions of Bnei Yisrael. I asked Rabbi Chaim Jachter about the origin within the Pasuk of the Mitzvah to proclaim each Rosh Chodesh. He answered that the first “Lachem” (“for you”) in the Pasuk teaches that it is up to us, Bnei Yisrael, and not Hashem, to determine when the beginning of each month will occur.
The Pirchei Levanon says that “Lachem” also teaches that Nissan is a time for all of Bnei Yisrael’s needs to be fulfilled; just as the first Nissan was the month of Geulah from Mitzrayim, so too all of our first months will be months of Geulah in which the needs of Bnei Yisrael will be fulfilled.
The Baal HaTurim teaches based on the fact that variations of the word “Chodesh” appear three times in this Pasuk that Rosh Chodesh Nissan is the Rosh HaShanah of three things. Firstly and most simply, Nissan is the first month of the year. The other two are based on Gematria. The Gematria of “Chodesh” is 312. Adding one as a Kolel (based on laws of Gematria) to this sum yields 313, equal to that of “LaRegalim,” “for holidays.” Thus, we see that Rosh Chodesh Nissan is also a Rosh HaShanah LaRegalim (see Rosh HaShanah 2a). For the final significance of Rosh Chodesh Nissan, we must take the Gematria of “Nissan” itself, 170. This is equal to the Gematria of “Melachim,” kings, showing that Rosh Chodesh Nissan is also Rosh HaShanah LaMelachim (ibid.). (Additionally, the letters of the repeated word “Lachem” in the Pasuk can be rearranged to form “Melech,” king.)
Rashi asks what the word “HaZeh,” “this,” has to do with the Mitzvah of Rosh Chodesh. He answers that Moshe was unsure of how much of the moon had to be visible, so Hashem showed him the moon that night, and told him “HaZeh” - specifically the amount of moon that was visible to Moshe is the minimum requirement for Rosh Chodesh.
The Sefat Emet points out that unlike other nations, Bnei Yisrael use the moon, which represents night and times of hardship, to determine our months; this teaches that we continue through our hardships and regenerate like the moon. Other nations and religions create their calendars based on the sun, which represents good times, signifying that they can survive only the good, but will fall apart in bad times. History supports this idea; other nations, like the Assyrians, Babylonians, Persians, Greeks, and Romans, are no longer in existence, but Jews are still around, notwithstanding others' many attempts to wipe us out.
Rosh Chodesh Nissan, like every Rosh Chodesh, is a time of revival and empowerment of Bnei Yisrael. May our careful observance of this Mitzvah bring Mashiach's so that we can celebrate Bnei Yisrael's first Mitzvah with all of Yisrael together.