God not only instructs Israel concerning the first Passover in Egypt; He also institutes a week-long festival to commemorate their exodus and freedom. They are coming out of the land of Egypt, so, symbolically, they are to abstain from all leaven–eating only unleavened bread. During the week-long festival, the Israelites are to have holy assemblies on both the first and last day of the week, not working on those days–except what is necessary to prepare food. This festival is to be annual and permanent throughout the generations of national Israel.
The Feast of Unleavened Bread, what we normally just refer to as Passover, is an important festival for all of God’s people–Jew and Gentile. Even though those who are not national Israelites are not commanded, here, to observe the festival every year, we recognize that in the First Century AD, Jesus becomes the true Passover Lamb. During the Festival, He eats the unleavened bread with His disciples, and explains that it represents His own body. The wine represents His own blood–which will be shed and painted on the cross (cf. Matthew 26:17-29). This will be done not only for Israel but for the whole world. Like Israel celebrates God’s deliverance from slavery in Egypt by observing the feasts, we remember Christ’s work on Calvary by observing the Eucharist, or the Lord’s Supper (or communion). Since Jesus is the true Passover lamb, since He is also the one who delivered Israel from Egypt, the Feast of Unleavened Bread has always been about Him. He does not redefine the meal on Holy Week. He clarifies it and finally delivers His people among the nations from the bondage sin.