OBEYING IS GREATER THAN VOLUNTEERING
The Shulchan Aruch, Orach Chaim siman 430 contains only one halacha “The Shabbos before Pesach is called Shabbos Hagadol because of the miracle that occurred.”
The miracle refers to the fact that on the tenth day of Nissan which was a Shabbos, our ancestors took sheep and brought them into their homes for the sake of sacrificing them five days later. The miracle was that in spite of the fact that the Egyptians worshiped the sheep none of the neighbors stopped us from collecting these sheep.