23 Eucharistic communion also confirms the Church in her unity as the body of Christ. Saint Paul refers to this unifying power of participation in the banquet of the Eucharist when he writes to the Corinthians: “The bread which we break, is it not a communion in the body of Christ? Because there is one bread, we who are many are one body, for we all partake of the one bread” ( 1 Cor 10:16-17). Saint John Chrysostom's commentary on these words is profound and perceptive: “For what is the bread? It is the body of Christ. And what do those who receive it become? The Body of Christ – not many bodies but one body. For as bread is completely one, though made of up many grains of wheat, and these, albeit unseen, remain nonetheless present, in such a way that their difference is not apparent since they have been made a perfect whole, so too are we mutually joined to one another and together united with Christ”. The argument is compelling: our union with Christ, which is a gift and grace for each of us, makes it possible for us, in him, to share in the unity of his body which is the Church. The Eucharist reinforces the incorporation into Christ which took place in Baptism though the gift of the Spirit (cf. 1 Cor 12:13, 27). The joint and inseparable activity of the Son and of the Holy Spirit, which is at the origin of the Church, of her consolidation and her continued life, is at work in the Eucharist. This was clearly evident to the author of the Liturgy of Saint James : in the epiclesis of the Anaphora, God the Father is asked to send the Holy Spirit upon the faithful and upon the offerings, so that the body and blood of Christ “may be a help to all those who partake of it ... for the sanctification of their souls and bodies”. The Church is fortified by the divine Paraclete through the sanctification of the faithful in the Eucharist.
Source: Ecclesia de Eucharistia (Vatican.va)