Keeping Sunday holy

At Sunday Mass, Christians relive with particular intensity the experience of the Apostles on the evening of Easter when the Risen Lord appeared to them as they were gathered together (cf. Jn 20:19). In a sense, the People of God of all times were present in that small nucleus of disciples, the first fruits of the Church. Through their testimony, every generation of believers hears the greeting of Christ, rich with the messianic gift of peace, won by his blood and offered with his Spirit: "Peace be with you!" Christ's return among them "a week later" (Jn 20:26) can be seen as a radical prefiguring of the Christian community's practice of coming together every seven days, on "the Lord's Day" or Sunday, in order to profess faith in his Resurrection and to receive the blessing which he had promised: "Blessed are those who have not seen and yet believe" (Jn 20:29). This close connection between the appearance of the Risen Lord and the Eucharist is suggested in the Gospel of Luke in the story of the two disciples of Emmaus, whom Christ approached and led to understand the Scriptures and then sat with them at table. They recognized him when he "took the bread, said the blessing, broke it and gave it to them" (24:30). The gestures of Jesus in this account are his gestures at the Last Supper, with the clear allusion to the "breaking of bread", as the Eucharist was called by the first generation of Christians.
 
-- Pope John Paul II
Dies Domini, paragraph 33