Incorporation into Christ, which is brought about by Baptism, is constantly renewed and consolidated by sharing in the Eucharistic Sacrifice, especially by that full sharing which takes place in sacramental communion. We can say not only that each of us receives Christ, but also that Christ receives each of us. He enters into friendship with us: “You are my friends” (Jn 15:14). Indeed, it is because of him that we have life: “He who eats me will live because of me” (Jn 6:57). Eucharistic communion brings about in a sublime way the mutual “abiding” of Christ and each of his followers: “Abide in me, and I in you” (Jn 15:4).
By its union with Christ, the People of the New Covenant, far from closing in upon itself, becomes a “sacrament” for humanity, a sign and instrument of the salvation achieved by Christ, the light of the world and the salt of the earth (cf. Mt 5:13-16), for the redemption of all. The Church's mission stands in continuity with the mission of Christ: “As the Father has sent me, even so I send you” (Jn 20:21). From the perpetuation of the sacrifice of the Cross and her communion with the body and blood of Christ in the Eucharist, the Church draws the spiritual power needed to carry out her mission. The Eucharist thus appears as both the source and the summit of all evangelization, since its goal is the communion of mankind with Christ and in him with the Father and the Holy Spirit.
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.
The gift of Christ and his Spirit which we receive in Eucharistic communion superabundantly fulfils the yearning for fraternal unity deeply rooted in the human heart; at the same time it elevates the experience of fraternity already present in our common sharing at the same Eucharistic table to a degree which far surpasses that of the simple human experience of sharing a meal. Through her communion with the body of Christ the Church comes to be ever more profoundly “in Christ in the nature of a sacrament, that is, a sign and instrument of intimate unity with God and of the unity of the whole human race”.
The seeds of disunity, which daily experience shows to be so deeply rooted in humanity as a result of sin, are countered by the unifying power of the body of Christ. The Eucharist, precisely by building up the Church, creates human community.