The plagues which came upon the Egyptians, as recorded in the book of Exodus, clearly resulted from their ruler's stubborn refusal to permit the Israelites to leave Egypt and worship their God in the wilderness. The final climactic stroke which brought Pharaoh and his people to their senses was the slaying of the eldest son of every Egyptian family in a single night. Even the firstborn of their animals were destroyed.
In anticipation of this dire event, it was revealed to Moses that the Israelites must go through the ritual of the Passover. This solemn feast appears to have been instituted with both consecration and protection in mind. Some scholars contend that a somewhat similar festival may have been known to the Hebrews prior to this time; but, if so, the deeper significance attached to it clearly dated from that dread midnight experience when the Egyptians felt the full impact of the message of the plagues.
On the tenth day of the month Nisan, sometimes termed Abib, which, according to the Christian calendar, corresponds to part of March and part of April and which was to be viewed henceforth as the first month of the Hebrew year, the Israelites were to begin their preparations by first selecting for the use of each household a yearling lamb or kid without blemish. It was to be sacrificed in the evening of the fourteenth day of the same month. With its blood, the doorposts and lintel of each Hebrew dwelling were to be clearly marked and thus identified.
