32 But you wonder at the event: even she herself who bare him wondered at this. For she says to Gabriel, How shall this be to me, since I know not a man? But he says, The Holy Ghost shall came upon you, and the power of the Highest shall overshadow you: wherefore also the holy thing which is to be born shall be called the Son of God. Immaculate and undefiled was His generation: for where the Holy Spirit breathes, there all pollution is taken away: undefiled from the Virgin was the incarnate generation of the Only-begotten.
And if the heretics gainsay the truth, the Holy Ghost shall convict them: that overshadowing power of the Highest shall wax angry: Gabriel shall stand face to face against them in the day of judgment: the place of the manger, which received the Lord, shall put them to shame. The shepherds, who then received the good tidings, shall bear witness; and the host of the Angels who sang praises and hymns, and said, Glory to God in the highest, and on earth peace among men of His good pleasure: the Temple into which He was then carried up on the fortieth day: the pairs of turtle-doves, which were offered on His behalf: and Symeon who then took Him up in his arms, and Anna the prophetess who was present.
Source: Catechetical Lectures (New Advent)