In Judaism, the holiday commemorating the liberation of the Hebrews from slavery in Egypt. Before sending a plague to destroy the firstborn of the Egyptians, God instructed Moses to tell the Israelites to place a special mark above their doors as a signal for the angel of death to pass over (i.e., spare the residents). The festival of Passover begins on the 15th and ends on the 22nd (in Israel, the 21st) day of the month of Nisan (March or April). During Passover only unleavened bread may be eaten, symbolizing the Hebrews' suffering in bondage and the haste with which they left Egypt. On the first night of Passover, a Seder is held, and the Haggadah is read aloud.