The holy Eucharist completes Christian initiation. Those who have been raised to the dignity of the royal priesthood by Baptism and configured more deeply to Christ by Confirmation participate with the whole community in the Lord's own sacrifice by means of the Eucharist.
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.
Catechism of the Catholic Church 1322, 1323
"The Church draws her life from the Eucharist. This truth does not simply express a daily experience of faith, but recapitulates the heart of the mystery of the Church. In a variety of ways she joyfully experiences the constant fulfilment of the promise: “Lo, I am with you always, to the close of the age” (Mt 28:20), but in the Holy Eucharist, through the changing of bread and wine into the body and blood of the Lord, she rejoices in this presence with unique intensity. Ever since Pentecost, when the Church, the People of the New Covenant, began her pilgrim journey towards her heavenly homeland, the Divine Sacrament has continued to mark the passing of her days, filling them with confident hope.
The Second Vatican Council rightly proclaimed that the Eucharistic sacrifice is “the source and summit of the Christian life”.1 “For the most holy Eucharist contains the Church's entire spiritual wealth: Christ himself, our passover and living bread. Through his own flesh, now made living and life-giving by the Holy Spirit, he offers life to men”.2 Consequently the gaze of the Church is constantly turned to her Lord, present in the Sacrament of the Altar, in which she discovers the full manifestation of his boundless love." (Pope John Paul II, Ecclesia de Eucharistia)