The LORD said to Moses and Aaron in the land of Egypt, “This month shall be for you the beginning of months. It shall be the first month of the year for you. Tell all the congregation of Israel that on the tenth day of this month every man shall take a lamb according to their fathers’ houses, a lamb for a household. And if the household is too small for a lamb, then he and his nearest neighbor shall take according to the number of persons; according to what each can eat you shall make your count for the lamb. Your lamb shall be without blemish, a male a year old. You may take it from the sheep or from the goats, and you shall keep it until the fourteenth day of this month, when the whole assembly of the congregation of Israel shall kill their lambs at twilight.
“Then they shall take some of the blood and put it on the two doorposts and the lintel of the houses in which they eat it. They shall eat the flesh that night, roasted on the fire; with unleavened bread and bitter herbs they shall eat it. Do not eat any of it raw or boiled in water, but roasted, its head with its legs and its inner parts. And you shall let none of it remain until the morning; anything that remains until the morning you shall burn. In this manner you shall eat it: with your belt fastened, your sandals on your feet, and your staff in your hand. And you shall eat it in haste. It is the LORD’s Passover. For I will pass through the land of Egypt that night, and I will strike all the firstborn in the land of Egypt, both man and beast; and on all the gods of Egypt I will execute judgments: I am the LORD. The blood shall be a sign for you, on the houses where you are. And when I see the blood, I will pass over you, and no plague will befall you to destroy you, when I strike the land of Egypt. (Exodus 12:1-13 ESV)
The tenth and final plague is the one that will deliver Israel from Egypt and marks the beginning of a new life for the nation, a life of freedom given by Yahweh, so this month (our March/April) constitutes the beginning of Israel’s new calendar. Every family or combination of families, in accord with how many people a lamb will feed, are to set aside a lamb on the 10th day of the month and observe it until the 14th day to make sure it is without blemish, then eat it on the 14th day. The lamb is first bled and its blood applied to the doorposts of each home where the lamb is eaten along with bitter herbs and unleavened bread. It must all be eaten and any remains burned and all this in readiness to leave Egypt immediately.
Unlike the other plagues in which God protected the people, in order to get protection from this plague each person must exercise faith in Yahweh by sacrificing the lamb and applying its blood. For their firstborn to live a lamb must die, a substitute that indicates that each of them deserves death, just like the Egyptians, but that God has covered their guilt with sacrifice of a guiltless one on their behalf. Where God sees blood He passes over and does not judge the inhabitants. All of this is to demonstrate His power and grace toward Israel and His judgment on Egypt and her gods.
We too have had a Passover lamb slain on our behalf, Jesus the one without blemish, and by trusting in His provision and sacrifice we have been passed over from judgment. Behold the lamb of God who takes away the sin of the world.
Every time I have gone to Ethiopia the group I have worked with has always closed our time of ministry with a slaying of a goat that provides our lunch. One goat feeds a lot of people and lunch happens remarkably quickly after the goat is killed (always by one of us foreigners). God binds people together through such an experience, and Passover, as He instituted it, was a communal experience, a taste of what salvation is and must be, a family context where those redeemed rejoice together.