This is the foundational feast. The 6 feasts that follow are built upon it. It is covered in Leviticus 23:5.
In all the words that are used to describe what took place in Egypt none fits better than one word – “Redemption”. Israel was redeemed so that they could worship and serve the true and living G-d. But this redemption is not without cost. Blood had to be shed. All of the lambs sacrificed in Egypt pointed to the one true Lamb of G-d which takes away the sin of the world (John 1:29).

The story of Passover begins in the book of Exodus. The children of Israel were slaves in Egypt, subjected to harsh labor and cruelty. G-d heard the cry of his people and sent Moses to tell Pharaoh to let G-d’s people go. However G-d hardened Pharaoh’s heart so that he would not listen, but G-d used this to perform many signs and wonders in Egypt. He sent plagues upon the Egyptians to spite their so-called gods and to show all that He is the one true G-d. 

After nine devastating plagues fell upon the Egyptians, G-d instructed his people to take an unblemished lamb, one for each household, keep it for three days, and then slaughter it and cover their doorposts with its blood. They were to take its meat, roast it by fire, and eat it with matza and bitter herbs, and not a single bone in its body was to be broken. That night G-d went through the land of Egypt and struck down every firstborn man and beast; however, every house which had the blood on the doorpost was spared.

This was how G-d redeemed his people from bondage in Egypt. The blood on the doorposts was a sign that they were his people.

It was this event that became the first Passover, for the destroyer passed over each house that was marked with the blood. This became an eternal ordinance, a reminder for every generation of what G-d did to deliver his people.

Fast forward hundreds of years later to find Yeshua observing the Passover Seder with his talmidim, an event also dubbed as the Last Supper, for that night Yeshua was taken into custody. He was beaten and interrogated, yet the only charge they could pin on him was admitting to being Mashiach Ben-Elohim. They could not find a true fault in him. 

In the book of John, it states that Yeshua was handed over to be crucified on the Day of Preparation for Pesach, and then died that afternoon -- at the same time the Passover lamb was to be slaughtered.

This was the ultimate act of redemption. 

It is through Yeshua’s atoning blood that all, Jew and Gentile alike, can go before G-d and repent for their sin. Just as the lamb’s blood was used in the first Passover to redeem Israel from Egypt, it is through Yeshua’s blood that we are redeemed and called G-d’s people.