The Shabbat preceding Passover (Pesah) is known as Shabbat ha-Gadol, “the Big Sabbath.” A number of imaginative reasons have been put forward for this name, but in truth it seems to have arisen from the practice of reviewing in public the things that needed to be done in preparation for the coming festival. (Before the time when ordinary people could afford books, such a review had to be done orally before the whole congregation, and the Shabbat preceding the festival was an apt occasion.) But going over all the laws and customs of Passover in synagogue could take quite a while, hence “the Big Sabbath.” In fact, a number of didactic poems were composed in the Middle Ages to help people remember the rules; hearing the same poem year after year, synagogue-goers would eventually come to recall them by heart.
This is in turn connected to a somewhat mysterious passage in the Haggadah that ends the Passover Seder in many Jewish homes, the evocative Hasal Seder Pesah. I’ve seen its lines translated in more or less the same way in quite a few haggadot, for example:
The order of the Passover service has been completed according to its precept, to all its law and its custom. As we have been privileged to have this Seder, may we have the merit to fulfill it in the future.
Ended is the Passover Seder, according to custom, statute, and law. As we were worthy to celebrate it this year, so may we perform it in future years.
Here’s a popular rhyming version:
Ended the act of the Pesach night/Each law and custom kept aright:/As we’ve lived to do it without a stain,/God grant we do it time and again.
These translations all slightly distort the words in order to make sense of their current placement in the Haggadah. But in Hebrew the text says: “Just as we have had the merit to arrange it (lesadder ‘oto), so may we have the merit to do it (la‘asoto).” Naturally, many people have been puzzled by these words: Didn’t we just finish doing it now, at the conclusion of the Seder? Then why should we be asking to do it sometime in the future? That is why the above translations all suggest that “to do it” refers to doing it again in future years (but of course it doesn’t say “again”). Other translations see in the phrase “to do it” a reference to performing the paschal sacrifice when the Jerusalem Temple is at last rebuilt.
Actually, these lines originally formed part of the ending of a lengthy didactic poem written in the eleventh century by the French scholar Joseph ben Samuel Bonfils (Tov ‘Elem). The poem was written to be recited on the Shabbat just preceding Passover, Shabbat ha-Gadol. Having set out in detail various aspects of the requirements of Passover, it concluded: “Just as we have been able to set it forth [that is, set forth this review of the laws of Passover on this Sabbath preceding the festival], so may we be able to perform it [in a few days on Passover itself].” In time, these lines were inserted at the end of the Haggadah, where they really didn’t fit.
In any case, reading the whole poem, which was originally incorporated into the Musaf Amidah of that Shabbat, certainly added to the overall length of the regular Shabbat service, as did other such reviews: “the Big Sabbath” was thus a fitting title for this day.