Dora Bas Rivka Silver O'H
The First Passover
G-d sent word through Moshe to Pharaoh that around midnight, He would kill every first-born male in Egypt, from Pharaoh's first-born to that of a lowly servant girl. Even the first-born animals would be affected by this plague. This will be an occasion of unprecedented mourning among the Egyptians, but the Jews won't suffer so much as a dog growling at them. This will cause the officers of Egypt to beg the Jews to leave, which they will.
After Moshe departed from Pharaoh, G-d told him that, true to form, the monarch wouldn't listen, which gives Him reasons to perform great wonders in Egypt. G-d then commanded the first Passover.
First, He decreed that Nisan, the month in which the Exodus was about to occur, would be the first month of the year for Jews. (Some people are confused as to why Rosh Hashana - the "Jewish New Year" - occurs in the seventh month. They really mark completely separate things.) Moshe communicated to the people that, on the tenth day of the month, they were to take a lamb or a kid per family unit and put it aside until the 14th of the month. Everyone should slaughter their animal that afternoon and paint their doorways with the blood. That night, they were to eat their sacrifices roasted, with matzah (unleavened bread) and maror (bitter herbs). The offering may not be cooked in water, only roasted. It had to be eaten that night; any leftovers were to be burned.
The Jews were to eat their Passover meals in haste, fully dressed and ready to depart. G-d would pass through Egypt that night and execute judgment on the Jews' oppressors and their idols. The Jews would be protected by the blood they painted on their doorposts; G-d would not permit "the destroyer" (mashchis) to touch them as He punishes Egypt. (If G-d is personally smiting Egypt, what's this "destroyer" that He won't let into the Jews' homes? That refers to the "angel of death." Every day, people die for a variety of reasons - accidents, illness, violence, etc. On that night, G-d protected the Jews against not only His plague, but even against otherwise "normal" deaths.)
G-d decreed that the Passover must be commemorated in perpetuity. The Jews are to eat matzah, to the exclusion of leavened bread, for a full week; all leaven must be cleaned out in advance. This is a serious commandment - eating leaven during the week of Passover would lead to spiritual excision (kareis). Furthermore, the first and last days of this week-long holiday would be festivals, on which labor is prohibited. The labor restrictions are similar to those of Shabbos, except that food preparation (ochel nefesh) is permitted.
The matzah must be guarded in its preparation and this holiday must be carefully observed. The rules apply equally to those born Jewish and to converts.