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 God. 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 God which takes away the sin of the world (John 1:29).