Courtesy of www.jewishappleseed.org/apple/passhist.htm
Passover is a holiday that celebrates the escape of the Israelites from Egypt in approximately 1225 B.C.E. The narrative of this adventure is told in the Biblical book of Exodus.
The Israelites had moved down into Egypt as long as 400 years earlier, according to the Bible. But some scholars suggest that the actual time span was probably closer to 200 years or less, based upon the Biblical genealogies from Joseph (who brought his own family into Egypt) to Aaron (who, with Moses, led the people out of Egypt).
The Israelites came down to Egypt during a time when a famine was raging in the Biblical Near East. Egypt had stockpiled food during the seven years of plenty that had preceded the famine. Joseph, one of the younger sons of the patriarch Jacob (who was also known as Israel) had predicted the years of plenty and the years of famine. As a result, he had a high position in the court of the Pharaoh. The Pharaoh welcomed Joseph's family and settled them in the delta region of Goshen, where they prospered.
For many generations, the Israelites enjoyed the protection of the Pharaohs, who valued their work as shepherds. However, a Pharaoh eventually came to power who feared the Israelites. According to the Book of Exodus, this Pharaoh tried to destroy the Israelite population by ordering all male Israelite infants to be killed at birth. He also required the Israelites to work on large-scale building projects without pay and under terrible working conditions. The Israelites saw themselves as slaves.
The book of Exodus tells us that God ordered Moses, a young Israelite man who had been raised in the palace of the Pharaoh as a son of Pharaoh's daughter, to lead the Israelites out of Egypt with the help of his brother Aaron. However, in order to do so, it was necessary for the Pharaoh to agree to the emigration of the Israelite population. Moses said to Pharaoh, "Let my people go." To which Pharaoh replied, "No."
A battle of wills ensued between the will of the God of the Israelites and the will of the Pharaoh, who was worshipped as a deity by the Egyptians. Ten plagues were visited upon the Egyptians, the last of which was the death of the first born of each family. God told the Israelites to slaughter a lamb as a paschal sacrifice and put the blood of the sacrifice on the doorposts of their homes so that the Angel of Death would pass over them on the night of the tenth plague.
After this night of terror, Pharaoh said that the Israelites could leave Egypt. Fearful that the Pharaoh would change his mind (which he subsequently did), the Israelites left as quickly as possible. Because of this, their bread did not have time to rise.
They fled and found themselves standing at the shore of the Red Sea with the Pharaoh's chariots close behind in pursuit. God parted the sea for them, and they walked across on dry land. When the chariots tried to follow, the iron wheels stuck in the soft sand, the waters closed over them, and they drowned. Miriam, the sister of Moses and Aaron led the women in dancing and singing in praise to God, who had performed this miracle on their behalf.
God told the Israelites that they should celebrate their liberation from slavery in Egypt each year with a seven-day festival during which they should eat only unleavened bread. Two days of this holiday were set aside as special days during which no work was to be done. The first night of the holiday was to be special and was to include the eating of the Paschal sacrifice (of the lamb), bitter herbs, and unleavened bread, and the telling of the story of the Exodus from Egypt.
Since very ancient times, Jews all over the world have assembled with family and friends on the night of the 15th of Nisan to celebrate the redemption of the Israelites from slavery in Egypt.