It is customary on Shabbos Hagadol to preview the hagadah, by reading from “avadim hayinu” until “mechaper al kol avonoseinu.” We do not find a special directive to prepare in such a strong way anywhere else (While the rishonim say that one should prepare all tefillos so that they should be fluent in one’s mouth, that is a different type of directive). The question is obvious: Why is this preparation necessary? In fact, it seems to me that most people are very fluent in the hagadah itself, as many times when I quote a piece of the hagadah, the people listening are quickly able to find its source.
Rav Tzadok Hakohen answers this question based on two premises that are a recurring theme throughout the yom tov of Pesach. Firstly, there is no end as to how much one could and should go into detail in regard to the mitzvah of sipur yetzias mitzrayim (kol hamarbeh, harei ze mishubach). Secondly, the kabbalists tell us that the word “pesach” comes from the idea that one’s mouth (“pe”) should speak (“sach”). This means that the exercise in mouthing the story of the Exodus from Egypt is an essential portion of our avodah on Pesach.
We also know that one’s actions during the week will affect the whole week and the Shabbos at the end of the week, and the way one observes the Shabbos infuses the upcoming week with an atmosphere reflecting the Shabbos that has passed. Hence, we understand that in order for this week to produce that which it is supposed to achieve, it is necessary to precede it with a Shabbos exercise in that direction. This is the meaning of the words “midei77 shabbas b’shabbato” – that each week is encapsulated in the week beforehand, for it is that previous Shabbos, which produces the ruchniyus energy of the upcoming week.
Therefore, if we would like to be successful on Seder night, we must not just rehearse the hagadah, but actually connect to it in a way that we are energized to repeat the story of the hagadah in a heartful and animated way.
So, this week, when some of us have already finished our physical preparations for Pesach (e.g. cleaning), we should keep in mind that the success of Pesach, and of seder night in particular, really starts today, Shabbos Hagadol. Therefore, we should realize, that the whole week preceding Pesach is our opportunity to make the seder night a success.