Yes it is not that they knew that then but isn't keeping the Passover remembrance of what God did for the Jews?
Luk 22:15 And he said unto them, With desire I have desired to eat this
passover with you before I suffer:
Luk 22:16 For I say unto you, I will not any more eat thereof, until it be fulfilled in the kingdom of God.
Luk 22:17 And he took the cup, and gave thanks, and said, Take this, and divide it among yourselves:
Luk 22:18 For I say unto you, I will not drink of the fruit of the vine, until the kingdom of God shall come.
Luk 22:19 And he took bread, and gave thanks, and brake it, and gave unto them, saying, This is my body which is given for you: this do in remembrance of me.
Luk 22:20 Likewise also the cup after supper, saying, This cup is the new testament in my blood, which is shed for you.