“You marvel at what has happened. Did she not also marvel who gave him birth, seeing that she said to Gabriel: “How will this happen since I do not know man?” (Lk 1:34). But he answered: “The Holy Spirit will come upon you, and the power of the Most High will cover you with its shadow; hence, the holy Child to be born will be called Son of God” (Lk 1:35).
Pure and spotless is this birth. For where the Holy Spirit breathes, all pollution is taken away, so that the human birth of the Only-be-gotten from the Virgin is undefiled.
If then, the heretics speak against the truth, the Holy Spirit himself will convict them; against them will rise the anger of the overshadowing power of the Most-High and, in the Day of Judgment, Gabriel will rise up against them with severity; the manger that held the Lord will reprove them. The shepherds who received the glad tidings, the host of angels who sang praises and hymns saying: “Glory to God in the highest and peace on earth to men of goodwill” (Lk 2:13-14), the temple into which he was brought after forty days, the pair of turtle doves offered for him, Simeon who took him in arms and the prophetess Anna who was present there: they will all bear witness against the heretics.”Cyril of Jerusalem, Catecheses 12, 34; PG 33, 768 A-769 A.
If we deny Him, all witnesses will speak against us. Man has no excuse to deny the incarnate God. Accepting and beliving in Jesus is doing His will.
Gambero, L., 1999. Mary and the Fathers of the Church 1st ed. Translated by Buffer, T., San Francisco: Ignatius Press. p. 140.