Question: Why is the Shabbos before Pesach called Shabbos HaGadol – the GREAT Shabbos? Secondly, why is there a custom to read or recite the bulk of the Magid section of the Haggadah (i.e. which recounts the story of Yetzias Mitzraim/the Exodus) on the afternoon of Shabbos HaGadol? (Not during the Rabbi’s drasha, of course!)
Answer: The reason dates back to the days preceding the Exodus. The 10th day of the month of Nisan occurred on Shabbos that year. Hashem had instructed that the head of each household take a lamb on that day, bring it to his home and tie it on to the bedpost to wait for the 14th of the month, at which time he would slaughter it for the Korban Pesach (Pesach offering). In those days, the Egyptians worshipped sheep. Imagine hoards of Jews parading down Main Street, leading the Egyptian diety with ropes. When asked by the idolaters what they are doing with the animals, the Jews reply, “Why, we are going to slaughter them to our G-d!” We would expect the Egyptians to declare war right then and there! Instead, they said nothing and just went about their business. One may not have realized it, but that silence was an open miracle, orchestrated by Hashem as just one more step in the Jews’ supernatural Redemption!
The Sages chose to commemorate this “miracle-before-the-miracles” by declaring the Shabbos before Pesach – no, not the 10th of Nisan per se – as Shabbos HaGadol – the Shabbos of the GREAT MIRACLE! The message is that the Geula (Redemption) really began on Shabbos, and that is why we read that part of the Haggadah on Shabbos!