Jesus is the Lamb of God, and even John the Batist testifies to this: “Lo, the Lamb of God, who taketh away the sins of the world.”
Jesus had to be the Paschal Lamb, or else He could not die for our sins, since God had instructed the Jews to make holocausts, which in turn were meant to point toward the Holy Sacrifice of Jesus, just as the serpent which Moses lifted up, and which drew all the Israelites to itself that they might be healed, was meant to point toward Jesus being lifted up on the Cross and drawing all men to Himself.
Because Jesus is the Lamb of God, He had to be the Paschal meal, the lamb which Jews are required to eat on the eve of Passover in remembrance of Israel’s freedom from bondage, in re-presentation of Israel’s flight from Egypt, and in anticipation of Israel’s awaited redemption (the three facets of Jewish holy days are remembrace, re-presentation, and anticipation, which is where we get the Mass from: remembrance of Jesus’ death. re-presentation of Calvary, and anticipation of the glory to come).
Hence, because His flesh had to be eaten and His blood drunk, He says during Passover, “Take and eat, this IS My Body…Take this, all of you, and drink from it; this IS the cup of My Blood.” He didn’t simply say “is” - though that would have been enough to show He meant the bread became His Body and the wine became His Blood - but emphasized the world “is,” as if to say, “Do not doubt, I am with you under the appearance of bread and wine, just as I am here at this table, and I will be with you always, even to the end of the ages.”
There is a Rabbinic tradition that states when the Messiah comes, all sacrifices will cease, save one: the thanksigiving offering. The Eucharist, which means “thanksigiving”, is truly the sacrifice of thanksgiving and praise, and since it is the one and same Holy Sacriifice of Jesus Christ on the Cross (the Lamb on the holy altar), then Jesus is truly present in the Eucharist, and just as He said, and as the Rabbinic tradition prophecies, “I will be with you always, even to the end of the ages”: The Eucharist will never cease, for it is the Sacrament of Christ.