The Eucharist is the Sign of the New Covenant

"But this is the covenant I will make with the house of Israel after those days—oracle of the LORD. I will place my law within them, and write it upon their hearts; I will be their God, and they shall be my people."  (Jeremiah 31: 33)

Write your law in my heart, O my God and then I will remember it at all times.

"Then he took a cup, gave thanks, and gave it to them, and they all drank from it.
He said to them, “This is my blood of the covenant, which will be shed* for many."  (Mark 14: 23 - 24)

The Eucharist is the everlasting covenant that Jesus Christ has left for us.