16 The saving efficacy of the sacrifice is fully realized when the Lord's body and blood are received in communion. The Eucharistic Sacrifice is intrinsically directed to the inward union of the faithful with Christ through communion; we receive the very One who offered himself for us, we receive his body which he gave up for us on the Cross and his blood which he “poured out for many for the forgiveness of sins” ( Mt 26:28). We are reminded of his words: “As the living Father sent me, and I live because of the Father, so he who eats me will live because of me” ( Jn 6:57). Jesus himself reassures us that this union, which he compares to that of the life of the Trinity, is truly realized. The Eucharist is a true banquet , in which Christ offers himself as our nourishment. When for the first time Jesus spoke of this food, his listeners were astonished and bewildered, which forced the Master to emphasize the objective truth of his words: “Truly, truly, I say to you, unless you eat the flesh of the Son of Man and drink his blood, you have no life within you” ( Jn 6:53). This is no metaphorical food: “My flesh is food indeed, and my blood is drink indeed” ( Jn 6:55).
Source: Ecclesia de Eucharistia (Vatican.va)