CATECHISM OF THE CATHOLIC CHURCH
SECOND EDITION

Paragraphs 1382–1386

1382 The Mass is at the same time, and inseparably, the sacrificial memorial in which the sacrifice of the cross is perpetuated and the sacred banquet of communion with the Lord's body and blood. But the celebration of the Eucharistic sacrifice is wholly directed toward the intimate union of the faithful with Christ through communion. To receive communion is to receive Christ himself who has offered himself for us.
1383 The altar, around which the Church is gathered in the celebration of the Eucharist, represents the two aspects of the same mystery: the altar of the sacrifice and the table of the Lord. This is all the more so since the Christian altar is the symbol of Christ himself, present in the midst of the assembly of his faithful, both as the victim offered for our reconciliation and as food from heaven who is giving himself to us. "For what is the altar of Christ if not the image of the Body of Christ?" asks St. Ambrose. He says elsewhere, "The altar represents the body [of Christ] and the Body of Christ is on the altar." The liturgy expresses this unity of sacrifice and communion in many prayers. Thus the Roman Church prays in its anaphora:

We entreat you, almighty God,
that by the hands of your holy Angel
this offering may be borne to your altar in heaven
in the sight of your divine majesty,
so that as we receive in communion at this altar
the most holy Body and Blood of your Son,
we may be filled with every heavenly blessing and grace.

1384 The Lord addresses an invitation to us, urging us to receive him in the sacrament of the Eucharist: "Truly, I say to you, unless you eat the flesh of the Son of man and drink his blood, you have no life in you."
1385 To respond to this invitation we must prepare ourselves for so great and so holy a moment. St. Paul urges us to examine our conscience: "Whoever, therefore, eats the bread or drinks the cup of the Lord in an unworthy manner will be guilty of profaning the body and blood of the Lord. Let a man examine himself, and so eat of the bread and drink of the cup. For any one who eats and drinks without discerning the body eats and drinks judgment upon himself." Anyone conscious of a grave sin must receive the sacrament of Reconciliation before coming to communion.
1386 Before so great a sacrament, the faithful can only echo humbly and with ardent faith the words of the Centurion: "Domine, non sum dignus ut intres sub tectum meum, sed tantum dic verbo, et sanabitur anima mea" ("Lord, I am not worthy that you should enter under my roof, but only say the word and my soul will be healed."). And in the Divine Liturgy of St. John Chrysostom the faithful pray in the same spirit:

O Son of God, bring me into communion today with your mystical supper. I shall not tell your enemies the secret, nor kiss you with Judas' kiss. But like the good thief I cry, "Jesus, remember me when you come into your kingdom."