The Shabbat before Passover is called Shabbat HaGadol—the Great Shabbat. This name indicates that this Shabbat possesses a particular grandeur compared to the other Shabbatot of the year. This grandeur is expressed in the Shulchan Aruch—the Code of Jewish Law: "For on this Shabbat a great miracle occurred." What was the miracle? The Egyptian firstborn saw the Jewish people preparing to offer the Passover sacrifice and heard that on Passover night God would kill them. When they demanded that their parents send the Jewish people away to escape the plague, and their parents refused, a war broke out between the Egyptian firstborn, their parents, and the rulers. King David wrote of this war in the Psalms: “It struck Egypt.” with their firstborn, "Because His goodness endures forever.".
We must understand the connection between that miracle and Shabbat, to the point that the miracle elevates Shabbat and transforms it from an "ordinary" Shabbat to a "Shabbat HaGadol" (Holy Shabbat). Furthermore, considering that Shabbat is inherently holy, a sign between God and the Jewish people, belonging exclusively to the Jewish people, etc., how could a civil war among Egyptians possibly add any grandeur to Shabbat?
The answer lies in the aforementioned verse from Psalms, "who struck Egypt with her firstborn," where God is praised "for His goodness endures forever." In the same chapter of Psalms, other things appear that, on a more superficial level, are actions of the Holy One, blessed be He, such as "who performs great wonders," "who makes the great lights...the sun...the moon." In each of these actions, we can, in a certain way, find God's goodness, and that is why the Psalmist repeats, after each of these references, "for His goodness endures forever." However, what does God's "goodness" have to do with a civil war among Egyptians?
This expresses the idea that not only the creation of the world and the miracles that transcend the barriers of nature are the work of God, but also that two factions fighting a civil war in Egypt, the most impure place on earth, is a Divine act. Since "there is nothing except Him," even these kinds of events are planned and directed by God.
The war that broke out between the Egyptian firstborn and their parents was not a simple fight between two sides, but a "great miracle" of God: everyone clearly saw that God controls the world, and when the time comes for the Jewish people to leave Egypt for freedom, even the Egyptians themselves are affected in such a way that they fight among themselves for Jewish redemption!.
This concept is directly linked to the essence of Shabbat. This day is a testament to the fact that God created the world and constantly guides it. However, this idea is restricted to the realm of faith: we believe That God created the world in six days and rested on the seventh. On Shabbat HaGadol, when the Egyptian firstborn fought to fulfill the Divine Will of bringing the Jewish people out of Egypt, this belief was transformed into a clear recognition, visible to the eyes of flesh and blood, and that is why this miracle brought greatness to Shabbat.
From this we can learn an important lesson in serving God: when a Jew performs the Divine Will, he makes the world ready for "great miracles," even the miracle of "striking Egypt with its firstborn.".
Adapted from Shulchan Shabbat
For me it is a blessing to receive this teaching and I thank the Eternal because people like you fill us with knowledge and bring us closer to the will of the Creator.