The Shabbos that precedes Pesach is known as Shabbos HaGadol, “theGreat Shabbos.” The Alter Rebbe1 offers the following reason for the name:

“The Shabbos before Pesach is called Shabbas HaGadol since a great miracle occurred on that day. For ... when the Jews took the lambs for their Paschal offerings on that Shabbos, the Egyptian firstborn assembled before them and inquired why they were doing so. The Jews responded: ‘This is our Paschal offering, for G‑d shall slay the Egyptian firstborn.’

“[Thereupon] the firstborn went to their fathers and to Pharaoh and demanded that they liberate the Jews. When they refused to do so, the firstborn declared war against the rest of the Egyptians and killed many of them. This is the meaning of the verse, ‘…Who struck Egypt through its firstborn....’2 It was instituted that this miracle be remembered in future generations on this Shabbos, which is therefore known as Shabbas HaGadol.

The Alter Rebbe’s words, “since a great miracle occurred on that day,” emphasizes the fact that the Shabbos is called “the Great Shabbos,” specifically because of the extraordinary nature of the miracle that took place. This, however, must be understood:

What was so “great” about this miracle, especially since the benefit the Jewish people derived from this miracle seems quite limited? For even though the firstborn “killed many of them,” the Jews were still unable to leave Egypt until after the “Plague of the Firstborn.” Why, then, is this event considered such a “great” miracle?

The Jewish people have often been miraculously saved from their enemies. To quote the text of the Haggadah: “In every generation there are those who rise against us to destroy us, and G‑d saves us from their hands.” Many of these miracles were accompanied by the death of a large number of our enemies, such as during the miracle at the Splitting of the Sea, the miracles of Chanukah and Purim, etc. In this regard, the miracle of Shabbas HaGadol is not unique.

The greatness of the miracle of Shabbas HaGadol, however, lies in the fact that our Egyptian enemies were destroyed by none other than the Egyptians themselves, rather than the Jewish people having to smite them. This takes on even greater significance when we realize that at that time, the Jewish people were still mired in exile, and Pharaoh emphatically refused to let them leave his land.

It was during this difficult time that the firstborn, the mightiest3 of the Egyptians and the greatest oppressors of the Jewish people, demanded that the Jews be set free. Moreover, the demands they made were so vociferous that they “declared war on the rest of the Egyptians and killed many of them.” The fact that the miracle took such a form caused it to be truly “great” — one not seen at any other time.

The salvation of the Jews from the hands of our enemies during the Splitting of the Sea and the miracles of Chanukah and Purim, etc., saw our enemies drowned in the sea or killed or vanquished by the Jewish people.

Here, however, it was the mightiest Egyptians themselves, the great persecutors and torturers of our people, who were miraculously transformed by G‑d into people who — while remaining Egyptians — took up the Jewish cause. This was a striking instance of “darkness being transformed into light.”

This event becomes even more remarkable when we realize that a miracle usually involves a change in the natural order of things. Understandably, if this change is so great that it “goes against nature,” even as “nature” is perceived by supranatural Torah, the miracle becomes even greater.

According to the natural Torah order, the more extreme forms of unholiness must be “cast aside” and shatteredrather than refined or elevated.4 Accordingly, for the unholy Egyptian firstborn to take up the holy cause of the Jewish slaves, this involved a change within the forces of nature even as the laws of nature are dictated by Torah — a very great miracle indeed,5 a miracle wherein G‑d demonstrated His unique deliverance.6

Based on Likkutei Sichos, Vol. XII, pp. 33-36.