The first element of eucharistic faith is the mystery of God himself, trinitarian love. In Jesus' dialogue with Nicodemus, we find an illuminating expression in this regard: "God so loved the world that he gave his only Son, that whoever believes in him should not perish but have eternal life. For God sent the Son into the world, not to condemn the world, but that the world might be saved through him" (Jn 3:16-17). These words show the deepest source of God's gift. In the Eucharist Jesus does not give us a "thing," but himself; he offers his own body and pours out his own blood. He thus gives us the totality of his life and reveals the ultimate origin of this love. He is the eternal Son, given to us by the Father. In the Gospel we hear how Jesus, after feeding the crowds by multiplying the loaves and fishes, says to those who had followed him to the synagogue of Capernaum: "My Father gives you the true bread from heaven; for the bread of God is he who comes down from heaven, and gives life to the world" (Jn 6:32-33), and even identifies himself, his own flesh and blood, with that bread: "I am the living bread which came down from heaven; if anyone eats of this bread, he will live forever; and the bread which I shall give for the life of the world is my flesh" (Jn 6:51). Jesus thus shows that he is the bread of life which the eternal Father gives to mankind.
 Post -Synodal Apostolic Exhortation of the Holy Father Benedict XVI on the Eucharist as the Source and Summit of the Church’s Life and Mission
 

The Church has received the Eucharist from Christ her Lord not as one gift – however precious – among so many others, but as the gift par excellence, for it is the gift of himself, of his person in his sacred humanity, as well as the gift of his saving work. Nor does it remain confined to the past, since “all that Christ is – all that he did and suffered for all men – participates in the divine eternity, and so transcends all times”.
When the Church celebrates the Eucharist, the memorial of her Lord's death and resurrection, this central event of salvation becomes really present and “the work of our redemption is carried out”.  This sacrifice is so decisive for the salvation of the human race that Jesus Christ offered it and returned to the Father only after he had left us a means of sharing in it as if we had been present there. Each member of the faithful can thus take part in it and inexhaustibly gain its fruits. This is the faith from which generations of Christians down the ages have lived. The Church's Magisterium has constantly reaffirmed this faith with joyful gratitude for its inestimable gift.  I wish once more to recall this truth and to join you, my dear brothers and sisters, in adoration before this mystery: a great mystery, a mystery of mercy. What more could Jesus have done for us? Truly, in the Eucharist, he shows us a love which goes “to the end” (cf. Jn 13:1), a love which knows no measure.

• Encyclical Letter of His Holiness Pope John Paul II on the Eucharist in its Relationship to the Church