If Christ had ceased to be man at his ascension — and it is to be feared that only too many Christians unreflectively assume that he did — then Mary would have ceased to be his mother, our incorporation into him would be a mere fiction, and so would our relation to him. But the Catholic doctrine of the Incarnation declares that the eternal Son of God, who at one moment in the world’s history took human nature in the womb of Blessed Mary, is, in that human nature, man for evermore. […] Mary is the mother of Jesus and of those who are incorporated into him, the mother of the Church which is his Mystical Body and which, because a man and his bride are one flesh, is also Christ’s bride.
The Incarnation took place at the Annunciation, when in response to Mary’s Fiat, the Word was made very man in her womb. But the further fact of her relation to the Church and its members had to wait for the Ascension and for the descent of the Spirit at Pentecost, when the Church, whose archetypal substance already existed in the manhood of Jesus, was fully and visibly constituted in power. In the Ascension the Lord’s human nature was withdrawn from human sight and touch. From then until Pentecost the apostolic group was the Church in expectancy and potentiality, awaiting its activation by the Spirit and the communication to it of the full reality of Christ’s manhood.
When the Spirit descended in tongues of fire, it was to make the waiting group into the mystical Body of Christ in a way analogous to that in which the descent of the Spirit upon Mary at her Annunciation had formed the natural body of Christ in her womb. Nevertheless, although the Mystical Body came into being by this new descent of the Spirit, there was not a new incarnation, Christ was not becoming man a second time, he was not assuming a new nature; the human nature which he had taken from his mother, in which he had died for our sins and risen again for our justification, was being made present under a new mode. There are not, strictly speaking, two bodies of Christ, a natural and a mystical, but one body of Christ which is manifested in two forms.
Nor does the story end here, for that part of the Mystical Body which is on earth needs to be continually nourished and sustained, as Christ’s natural body did before its glorification. It is through the Eucharistic Body of the Blessed Sacrament that this takes place. Here again, there is not a new incarnation, but in the Eucharist the human nature which Christ took from his mother is made present in yet another form, a form through which that part of the Mystical Body which is still in via on earth is repeatedly sustained and renewed.
In all these modes of manifestation, the human nature of Christ is the human nature which he took from Mary. The descent of the Holy Spirit on Mary at the Annunciation first formed it, the descent of the Holy Spirit upon the Apostles at Pentecost released it, so to speak, in the world as the Mystical Body of the Church, and the descent of the Holy Spirit upon the Eucharistic elements brings it to us as the Sacramental Body.
But in all these manifestations and expressions, it is one and the same Body, the Body which was formed in Mary’s womb, and so when we return from the Altar, having received the sacramental Body of Christ and having thereby been received more firmly into his Mystical Body, we can say with a new emphasis the words that, in the Genesis story, Adam said after he had tasted the food given him by the first Eve: ‘The woman gave me, and I did eat’ (Gen 3:12).
For it is the very body, the human nature, which Christ took from his mother, on which we are fed in the Holy Eucharist.
And Jesus and his members are one Body, the Whole Christ, and Mary is his mother and theirs.