Passover commemorates the deliverance of the Israelites from Egypt and the ‘passing over’ of their firstborn when Jehovah destroyed the firstborn of Egypt. Seasonally, it fell at the beginning of the barley harvest.​—Ex 12:14, 24-47; Le 23:10.

Passover was a memorial celebration; therefore the Scriptural command was: “And it must occur that when your sons say to you, ‘What does this service mean to you?’ then you must say, ‘It is the sacrifice of the passover to Jehovah, who passed over the houses of the sons of Israel in Egypt when he plagued the Egyptians, but he delivered our houses.’”​—Ex 12:26, 27.

At the Passover in Egypt, the head of the family was responsible for the slaying of the lamb (or goat) at each home, and all were to stay inside the house to avoid being slain by the angel. The partakers ate in a standing position, their hips girded, staff in hand, sandals on so as to be ready for a long journey over rough ground (whereas they often did their daily work barefoot). At midnight all the firstborn of the Egyptians were slain, but the angel passed over the houses on which the blood had been spattered. (Ex 12:11, 23) Every Egyptian household in which there was a firstborn male was affected, from the house of Pharaoh himself to the firstborn of the prisoner. It was not the head of the house, even though he may have been a firstborn, but was any male firstborn in the household under the head, as well as the male firstborn of animals, that was slain.​—Ex 12:29, 30; see FIRSTBORN, FIRSTLING.

The Ten Plagues upon Egypt all proved to be a judgment against the gods of Egypt, especially the tenth, the death of the firstborn. (Ex 12:12) For the ram (male sheep) was sacred to the god Amon-Ra, so that splashing the blood of the Passover lamb on the doorways would be blasphemy in the eyes of the Egyptians. Also, the bull was sacred, and the destruction of the firstborn of the bulls would be a blow to the god Osiris. Pharaoh himself was venerated as a son of Ra. The death of Pharaoh’s own firstborn would thus show the impotence of both Ra and Pharaoh.