Blood on the doorframe and the meal Christ said was about him
The Passover is the night Israel becomes Israel. Egypt has refused nine times to let the people go. The tenth plague will be the firstborn of every household in the land of Egypt, both human and animal. The LORD instructs Israel through Moses: take a lamb without blemish, one per household, on the tenth day of the first month. Keep it until the fourteenth day. Kill it at twilight. Daub the blood on the lintel and the two doorposts. Roast the lamb, eat it that night with unleavened bread and bitter herbs, with belts on and sandals on and staffs in hand. When the destroying angel passes through, he will see the blood and pass over the house. (Exodus 12)
The theological substance is in three motions. Substitution: the lamb dies so the firstborn does not. Identification: the blood on the door marks the household as belonging to the LORD's covenant rather than to Pharaoh's. Memorial: the meal will be repeated every year, perpetually, as a teaching ritual — the children will ask "What does this mean?" and the answer will be the story of the night the LORD passed through Egypt.
The Christian reading of the Passover begins in the Last Supper. Christ chooses the Passover meal to institute the new covenant. The bread is his body. The cup is his blood. The exodus from Egypt is the figure; the exodus from sin and death is the reality. Paul names Christ as "our Passover lamb" without explanation, as if the identification needed none: "For Christ, our Passover lamb, has been sacrificed." (1 Corinthians 5:7) The Synoptic Gospels are clear that the Last Supper is a Passover meal. The Gospel of John times the crucifixion to the killing of the Passover lambs on Nisan 14. Both timing frames preach the same gospel: Christ is the lamb whose blood marks the doorposts of the new covenant household.
The Passover does not stop being Jewish in the Christian reading. The continuity is the point. The Lord's Supper is the Passover meal kept in its messianic fulfillment, not a separate ritual the Christian church invents on its own. The Eastern liturgical traditions have preserved this most clearly — the Pascha is celebrated as the Christian Passover, the language of "passing over" from death to life carried straight from Exodus 12 into the resurrection narrative.
The Passover has also become the typological frame for almost every other sacrificial moment in Scripture. The lamb without blemish (Exodus 12:5) becomes the criterion for every offering Leviticus regulates. John the Baptist names Christ as "the Lamb of God who takes away the sin of the world" (John 1:29). The book of Revelation centers its heavenly worship on a slain lamb who is also a king. Every one of these is reading the Passover lamb forward.
The modern Jewish Passover seder is structured around the haggadah — the retelling of the exodus story, the four questions asked by the youngest child, the eating of bitter herbs and matzah and the symbolic cups of wine. Christians reading the seder will see references to the Christ they confess that the rabbinical tradition does not name. The editorial position is to honor the seder as the Jewish Passover, hold it carefully, and not appropriate it as a Christian liturgy in disguise.
Related entries: The Exodus, Heavenly Temple Naos, Table of Bread Presence