The Shabbos that precedes the festival of Pesach is known as Shabbos HaGadol , “The Great Shabbos,” commemorating as it does the miracle that transpired on the tenth of Nissan , which that year fell on a Shabbos, just prior to the Exodus.

Many Rabbis have asked1 why the commemoration of this day was assigned to Shabbos, rather than to the tenth of month, as is the case with all other festivals, which are celebrated on the monthly anniversary and not on the anniversary of the day of the week?

The relationship of the miracle of Shabbos HaGadol to the day of the week will be understood in light of the inner reason for all other festivals being celebrated according to the date of the month.

The difference between the days of the week and the days of the month is that the days of the week are bound up with creation and the world itself — “For in six days G‑d made the heavens and the earth, and on the seventh day He ceased from work and rested.”2

The concept of a “month,” however, is a later addition to and an elevation of creation. As our Sages state:3 “When G‑d chose His world, He [then] established within it new months.” Thus, months are not bound up with creation and nature, but with G‑d’s choice, and as such denote an additional degree of Divine activity “within His world.”

The difference between days of the week and days of the month is also related to the very nature of weeks and months: weeks, composed as they are of a seven-time cycle of day and night, are related to the sun, while the days of the Jewish month are related to the cycle of the moon.4

The illumination of the sun is a constant, and as such is similar to the unchanging quality of nature, while moonlight, which is always in a state of flux, symbolizes a novel aspect of creation — the state of miracles that transcends nature.

Since all Jewish holidays and festivals celebrate miraculous events — particular revelations of G‑dliness that transcend nature5 — it follows that they are celebrated according to the days of the month — the aspect which is novel and changing.

The reason why the miracle of Shabbos HaGadol is not celebrated in accordance with the day of the week will be understood accordingly.

The Alter Rebbe explains the miracle of Shabbos HaGadol in the following manner:6 “When the Jews took their Paschal lambs on that Shabbos, the first-born Egyptians gathered round and asked them why they were doing so. They told them that it was for the festival of Pesach, at which time G‑d would smite all the Egyptian first-born.

“The first-born thereupon went to their parents and to Pharaoh and requested that they send the Jews out of Egypt. When their demand was refused, the first-born engaged them in battle and killed many of them. Thus the verse states:7 ‘Who struck Egypt through its first-born.’ ”

At first glance, the entire incident seems wholly natural: After having witnessed the previous nine plagues, it is no wonder that the first-born believed they were about to be smitten. Thus, when their elders refused to allow the Jews to leave, it was natural that they killed many of them.

Thus, the miracle of Shabbos HaGadol lay not in overpowering the force of nature with a revelation of the supernatural, but merely that nature itself should undergo a change: Rather than opposing the exodus of the Jewish people, the first-born (the most powerful Egyptian oppressors)8 they did all they could to have the Jews depart.

The miracle of Shabbos HaGadol is therefore specifically linked to the days of the week — the course of nature — for it involved a change within nature itself. This is why it is always celebrated on Shabbos rather than on the tenth of Nissan , for it specifically relates to “days” rather than “months.”

Based on Likkutei Sichos, Vol. XXVII, pp. 44-46.