The Shabbat before Passover is called Shabbat Hagadol, "The Great Shabbat," because of a "great miracle" that occurred on this day. The Midrash relates that on this day—four days before the actual Exodus—the firstborn of Egypt, who constituted the religious and political elite of Egyptian society, demanded of Pharaoh that he free the Children of Israel. They even fought a war against Pharaoh's troops in an attempt to force the Israelites' liberation.

As a rule, important dates on the Jewish calendar are celebrated according to the day of the month: the Exodus is commemorated on the 15th of Nissan, the miracle of Chanukah on the 25th of Kislev, and so on. The war of the firstborn occurred on the 10th of Nissan, which on that year, was also the Shabbat before Passover. So why does the commemoration of this miracle follow the day of the week rather than the day of the month?

The answer to this question lies in another question: What was the miracle? The firstborn's rebellion did not achieve anything. We remained in Egypt until the 15th of Nissan, when the tenth and final plaque finally forced Pharaoh to set us free. It was G‑d who forced Pharaoh's hand, not the Egyptian firstborn. So what are we celebrating?

In truth, however, there are two types of miracles. The first type—which is the kind we usually imagine when we hear the word "miracle"--is about a result. There is a certain situation, and then something extraordinary happens to change it. A mortally ill person is miraculously healed. A desperately poor individual gets rich. An enslaved people is set free. And so on.

The second kind of miracle is about process rather than result. What happens is that the way things operate is transformed. The results may not be visible yet, but something very deep and fundamental has changed.

The second type of miracle may be less obvious and harder to appreciate, but it is infinitely greater. It doesn't just change what happened, but how things happen. It alters not a specific, incidental event, but the inner workings of the prevalent reality.

Such a miracle was the miracle of the "Great Shabbat." To reach down from heaven and smash the might of Egypt is one thing; but when Egypt itself—indeed, the most powerful stratum of Egyptian society—fights to liberate us from Egyptian slavery, that, in a way, is an even greater miracle than the Exodus itself.

The first type of miracle belongs to the month, which in the Jewish calendar follows the moon's rebirth from darkness every 29.5 days, and thus represents visible, radical change. The second miracle belongs to the weekly cycle, which represents the regular workings of nature. On the "Great Shabbat" we commemorate and re-experience the unique value of change from within, of change that affects not only the way things are but the very nature of reality.