Passover
Passover is the celebration of the Lord's liberation of the Israelites from bondage in Egypt. To mark which of God's people would be saved, God instructed Moses to have the people sacrifice a year-old lamb, sprinkle its blood on the doorpost of their house, and consume the lamb according to specific sacrificial instructions.
Jesus extended the Passover salvation of the Israelites to all peoples with his sacrifice on the Cross. Thus, Passover was a prefiguration" (an example of what was to come) of Christ. On Holy Thursday at the Lord's Supper, Jesus initiated the Sacrament of the Eucharist and declared the New Covenant with Man through is body and blood.
The Lord instructed Moses and Aaron,
This day will be a day of remembrance for you, which your future generations will celebrate with pilgrimage to the LORD; you will celebrate it as a statute forever. (Ex 12:14)
Thus Passover was to be a continuing event, just as salvation and redemption shall continue until the End of Time.
Christians celebrate the Passover at every Mass.