“This day shall be for you a memorial day, and you shall keep it as a feast to the LORD; throughout your generations, as a statute forever, you shall keep it as a feast. Seven days you shall eat unleavened bread. On the first day you shall remove leaven out of your houses, for if anyone eats what is leavened, from the first day until the seventh day, that person shall be cut off from Israel. On the first day you shall hold a holy assembly, and on the seventh day a holy assembly. No work shall be done on those days. But what everyone needs to eat, that alone may be prepared by you. And you shall observe the Feast of Unleavened Bread, for on this very day I brought your hosts out of the land of Egypt. Therefore you shall observe this day, throughout your generations, as a statute forever. In the first month, from the fourteenth day of the month at evening, you shall eat unleavened bread until the twenty-first day of the month at evening. For seven days no leaven is to be found in your houses. If anyone eats what is leavened, that person will be cut off from the congregation of Israel, whether he is a sojourner or a native of the land. You shall eat nothing leavened; in all your dwelling places you shall eat unleavened bread.” (Exodus 12:14-20 ESV)
What Yahweh is about to enact to rescue Israel must be memorialized each year in a feast, the Feast of Passover and Unleavened Bread. On the 14th of this month, which today is called Nisan, the Jews are to eat the lamb with unleavened bread and bitter herbs, reminding them that they had to leave Egypt in haste and for the next seven days they must eat unleavened bread as well. Leaven represented the old life in Egypt where they took from week to week that lump of dough that was starter dough for their next loaves of bread. They must get rid of that old dough and start all over with new leaven. Failure to do so would result in a death penalty.
Why such a serious requirement surrounding a meal? Because God knows how powerfully a re-enacted rite such as this is to forming our understanding of and remembrance of what matters most, that is, His absolute sovereign redemption of a helpless and undeserving people. Everything in our lives must rotate around this great reality, that God has saved us, not by our own doing, but by the provision of a substitute to cover our sin and guilt, so that we might walk in His power toward all the world.
For us as Christians the re-enactment we observe is rooted in the Passover, the very meal Jesus was observing with his disciples the night he was betrayed, in which he gave significance to the elements of the meal consistent with him being the Passover lamb. His is the sacrifice that covers our sin and enables God to freely forgive us and redeem us if we apply it to ourselves, as the Israelites applied the blood to their doorposts.
“Behold, the Lamb of God who takes away the sin of the world.” John 1:29