Mystery of The Eucharist.

For Christ did not enter a holy place made by hands, a mere copy of the true one, but into heaven itself, now to appear in the presence of God for us; nor was it that He would offer Himself often, as the high priest enters the Holy Place year by year with blood that is not his own. Otherwise, He would have needed to suffer often since the foundation of the world; but now once at the consummation of the ages He has been revealed to put away sin by the sacrifice of Himself.

Hebrews 9:24–25 NASB 

Jesus interrupted their Seder meal, celebrating Passover. Using unleavened bread and a cup of wine, he instituted the Lord’s Supper.