-- Heb 11:1-2, 8-19
The Annunciation to Mary inaugurates "the fullness of time", the time of the fulfillment of God's promises and preparations. Mary was invited to conceive him in whom the "whole fullness of deity" would dwell "bodily". The divine response to her question, "How can this be, since I know not man?", was given by the power of the Spirit: "The Holy Spirit will come upon you."
-- CCC 484
Art: Fra Angelico, Annunciation, Cortona Altarpiece, Museo Diocesano, Cortona, Italia.