From the Catechism of the Catholic Church:
1323 “At the Last Supper, on the night he was betrayed, our Savior instituted the Eucharistic sacrifice of his Body and Blood. This he did in order to perpetuate the sacrifice of the cross throughout the ages until he should come again, and so to entrust to his beloved Spouse, the Church, a memorial of his death and resurrection: a sacrament of love, a sign of unity, a bond of charity, a Paschal banquet ‘in which Christ is consumed, the mind is filled with grace, and a pledge of future glory is given to us.'”133
1337 The Lord, having loved those who were his own, loved them to the end. Knowing that the hour had come to leave this world and return to the Father, in the course of a meal he washed their feet and gave them the commandment of love.161 In order to leave them a pledge of this love, in order never to depart from his own and to make them sharers in his Passover, he instituted the Eucharist as the memorial of his death and Resurrection, and commanded his apostles to celebrate it until his return; “thereby he constituted them priests of the New Testament.”162
1338 The three synoptic Gospels and St. Paul have handed on to us the account of the institution of the Eucharist; St. John, for his part, reports the words of Jesus in the synagogue of Capernaum that prepare for the institution of the Eucharist: Christ calls himself the bread of life, come down from heaven.163
1339 Jesus chose the time of Passover to fulfill what he had announced at Capernaum: giving his disciples his Body and his Blood:
Then came the day of Unleavened Bread, on which the passover lamb had to be sacrificed. So Jesus sent Peter and John, saying, “Go and prepare the passover meal for us, that we may eat it….” They went … and prepared the passover. and when the hour came, he sat at table, and the apostles with him. and he said to them, “I have earnestly desired to eat this passover with you before I suffer; for I tell you I shall not eat it again until it is fulfilled in the kingdom of God.”…. and he took bread, and when he had given thanks he broke it and gave it to them, saying, “This is my body which is given for you. Do this in remembrance of me.” and likewise the cup after supper, saying, “This cup which is poured out for you is the New Covenant in my blood.”164
1340 By celebrating the Last Supper with his apostles in the course of the Passover meal, Jesus gave the Jewish Passover its definitive meaning. Jesus’ passing over to his father by his death and Resurrection, the new Passover, is anticipated in the Supper and celebrated in the Eucharist, which fulfills the Jewish Passover and anticipates the final Passover of the Church in the glory of the kingdom.
“Do this in memory of me”
1341 The command of Jesus to repeat his actions and words “until he comes” does not only ask us to remember Jesus and what he did. It is directed at the liturgical celebration, by the apostles and their successors, of the memorial of Christ, of his life, of his death, of his Resurrection, and of his intercession in the presence of the Father.165
1342 From the beginning the Church has been faithful to the Lord’s command. of the Church of Jerusalem it is written:
They devoted themselves to the apostles’ teaching and fellowship, to the breaking of bread and the prayers…. Day by day, attending the temple together and breaking bread in their homes, they partook of food with glad and generous hearts.166
1343 It was above all on “the first day of the week,” Sunday, the day of Jesus’ resurrection, that the Christians met “to break bread.”167 From that time on down to our own day the celebration of the Eucharist has been continued so that today we encounter it everywhere in the Church with the same fundamental structure. It remains the center of the Church’s life.
1344 Thus from celebration to celebration, as they proclaim the Paschal mystery of Jesus “until he comes,” the pilgrim People of God advances, “following the narrow way of the cross,”168 toward the heavenly banquet, when all the elect will be seated at the table of the kingdom.