Mascall’s insightful meditation connecting the Annunciation and Pentecost illustrates his devotion to the eternal mystery of the Incarnation.
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 model. 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…
…In all these modes of manifestation, the human nature of Christ is the human nature that 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.
(From E.L. Mascall, “Theotokos: The Place of Mary in the Work of Salvation,” in The Blessed Virgin Mary. Essays by Anglican Writers, ed. by E.L. Mascall and H.S. Box (Darton, Longman, and Todd, 1963) (H/T: Rev. Dr. Zachary Guiliano)