Catechism of the Catholic Church
787 From the beginning, Jesus associated his disciples with his own life, revealed the mystery of the Kingdom to them, and gave them a share in his mission, joy, and sufferings. 215 Jesus spoke of a still more intimate communion between him and those who would follow him: "Abide in me, and I in you.... I am the vine, you are the branches." 216 And he proclaimed a mysterious and real communion between his own body and ours: "He who eats my flesh and drinks my blood abides in me, and I in him." 217
788 When his visible presence was taken from them, Jesus did not leave his disciples orphans. He promised to remain with them until the end of time; he sent them his Spirit. 218 As a result communion with Jesus has become, in a way, more intense: "By communicating his Spirit, Christ mystically constitutes as his body those brothers of his who are called together from every nation." 219
789 The comparison of the Church with the body casts light on the intimate bond between Christ and his Church. Not only is she gathered around him; she is united in him, in his body. Three aspects of the Church as the Body of Christ are to be more specifically noted: the unity of all her members with each other as a result of their union with Christ; Christ as head of the Body; and the Church as bride of Christ.
English Translation of the Cathechism of the Catholic Church for the United States of America © 1997, United States Catholic Conference, Inc.