On the Shabbat before the Exodus--Nissan 10th on that year--the first-born of Egypt, who occupied the senior positions in the priesthood and government, fought a bloody battle with Pharaoh's troops, in an effort to secure the release of the Israelites and prevent the Plague of the Firstborn. This "great miracle" is commemorated each year on the Shabbat before Passover, which is therefore called Shabbat HaGadol, "The Great Shabbat." (This is one of the rare instances in which a commemorative date in the Jewish calendar is set by the day of the week rather than the day of the month.)
For more on the war of the Firstborn, see here.
Rabbi Moses ben Maimon, Talmudist, Halachist, physician, philosopher and communal leader, known in the Jewish world by the acronym "Rambam" and to the world at large as "Maimonides", was born in Cordova, Spain, on the 14th of Nissan of the year 4895 from creation--1135 of the Common Era [more...]
From the morning of Nissan 14 until the end of the festival of Passover--approximately eight days and eight hours--it is strictly forbidden to eat any leavened foods ("chametz") or anything containing the slightest trace of leaven. The deadline for eating chametz is two "seasonal hours" before midday--click here for the chametz eating deadline for your location.
When Nissan 14 falls on Shabbat--as it does this year--the Shabbat services and the Shabbat morning meal are held early in the day, so that the Shabbat meal, which requires two challah loaves (which are chametz), can be concluded before the deadline.
Make sure that you eat all the chametz that has been left for Shabbat before the deadline, as chametz cannot be sold, burned, or taken out to the street, etc., on Shabbat. For this reason, it is best to rid oneself of all chametz in one's possession before Shabbat, leaving only a small amount of challah for the Shabbat meal, and using kosher-for-Passover food and utensils for the rest of the meal. The remaining challah pieces and crumbs should be flushed down the toilet.
See the Getting-Rid-of-Chametz Wizard for more detailed instructions.
Links:
A Speck of Flour
The Escape Hatch
More about Leaven
Recite the chametz nullification statement disavowing all ownership of any chametz you may have missed in the getting-rid-of-chametz process. The "nullification" should be said no later than one "proprtionall hour" before midday--click here for the precise time for your location.
The Shabbat before Passover is termed Shabbat HaGadol ("The Great Shabbat") in commemoration of the "great miracle" that happened in Egypt on this day, heralding the Exodus from Egypt five days later (see "Today in Jewish Hstory"). Shabbat HaGadol customs include reading a portion of the Haggadah (from "Avadim hayinu..." to "...al kol avonotainu"), which tells the story of the Exodus; it is also customary that the rabbi of the community delivers a lecture in which he elaborates on the laws of Passover and their significance, in preparation for the festival.
When the Holy Temple stood in Jerusalem, the Passover offering was brought there on the afternoon of Nissan 14. Today it is commemorated by our recitation of the "Order of the Passover Offering" this afternoon, by the "shankbone" placed on the seder plate this evening, and the afikoman -- a portion of matzah eaten in its stead at the end of the seder meal.
Links: About the Passover offering
The 8-day festival of Passover--also called "The Festival of Matzahs" and "The Time of Our Freedom"--begins tonight at nightfall.
In the evening, we conduct a seder ("order") -- a 15-part ritualistic feast that encompasses the observances of the Passover festival: telling our children the story of the Exodus as described and expounded in the Haggadah; eating the matzah (unleavened bread), the bitter herbs dipped in charoset, and the afikoman (an additional portion of matzah eaten as "dessert" in commemoration of the Passover offering); drinking the four cups of wine; and numerous other symbolic foods and rituals commemorating both our slavery in Egypt and our liberation on this night.
Links:
www.Passover.org includes
a Seder guide, text of the Haggadah, in-depth studies, and more
The Seder Wizard is a step-by-step guide
to conducting the Seder