First, the Body of Christ refers to the human body of Jesus Christ, who is the divine Word become man. During the Eucharist, the bread and wine become the Body and Blood of Christ. As human, Jesus Christ has a human body, a resurrected and glorified body that in the Eucharist is offered to us in the form of bread and wine. Secondly, as St. Paul taught us in his letters, using the analogy of the human body, the Church is the Body of Christ, in which many members are united with Christ their head (1 Cor 10:16-17, 12:12-31; Rom 12:4-8). This reality is frequently referred to as the Mystical Body of Christ. All those united to Christ, the living and the dead, are joined together as one Body in Christ. This union is not one that can be seen by human eyes, for it is a mystical union brought about by the power of the Holy Spirit.
The Mystical Body of Christ and the eucharistic Body of Christ are inseparably linked. By Baptism we enter the Mystical Body of Christ, the Church, and by receiving the eucharistic Body of Christ we are strengthened and built up into the Mystical Body of Christ. The central act of the Church is the celebration of the Eucharist; the individual believers are sustained as members of the Church, members of the Mystical Body of Christ, through their reception of the Body of Christ in the Eucharist. Playing on the two meanings of “Body of Christ,” St. Augustine tells those who are to receive the Body of Christ in the Eucharist: “Be what you see, and receive what you are” (Sermon 272). In another sermon he says, “If you receive worthily, you are what you have received” (Sermon 227).
The work of the Holy Spirit in the celebration of the Eucharist is twofold in a way that corresponds to the twofold meaning of “Body of Christ.” On the one hand, it is through the power of the Holy Spirit that the risen Christ and his act of sacrifice become present. In the eucharistic prayer, the priest asks the Father to send the Holy Spirit down upon the gifts of bread and wine to transform them into the Body and Blood of Christ (a prayer known as the epiclesis or “invocation upon”). On the other hand, at the same time the priest also asks the Father to send the Holy Spirit down upon the whole assembly so that “those who take part in the Eucharist may be one body and one spirit” ( Catechism, no. 1353). It is through the Holy Spirit that the gift of the eucharistic Body of Christ comes to us and through the Holy Spirit that we are joined to Christ and each other as the Mystical Body of Christ. By this we can see that the celebration of the Eucharist does not just unite us to God as individuals who are isolated from one another. Rather, we are united to Christ together with all the other members of the Mystical Body. The celebration of the Eucharist should thus increase our love for one another and remind us of our responsibilities toward one another.
Furthermore, as members of the Mystical Body, we have a duty to represent Christ and to bring Christ to the world. We have a responsibility to share the Good News of Christ not only by our words but also by how we live our lives. We also have a responsibility to work against all the forces in our world that oppose the Gospel, including all forms of injustice. The Catechism of the Catholic Church teaches us: “The Eucharist commits us to the poor. To receive in truth the Body and Blood of Christ given up for us, we must recognize Christ in the poorest, his brethren” (no. 1397).