Exodus has been leading up to this event: The Passover - when the people of Israel were actually freed from slavery.
God has done incredible things for us, His children. But we tend to forget all that He has done for us... so He gave us reminders.
The Israelites were given Passover so that they would be able to remember how God saved them from slavery.
We have the Lord's Supper to help us remember how God has freed us from sin.
