A comment on the Old Testament prophecy “Therefore the Lord Himself will give you a sign: behold, the virgin shall conceive and bear a Son, and you shall call His name Immanuel” (Is 7:14)
“Let us read, then, the Scripture: “Ask for a sign from the Lord your God, in the depths or in the heights” (Is 7:11). Now then, a sign has to be something extraordinary. For the water from the rock was a sign, and the parting of the sea, and the turning back of the sun, and things of that sort. But what I am about to say has greater argumentative force against the Jews: . . the prophecy happened within the sixteen years [of Ahaz’s reign], Hezekiah was born at least nine years earlier. What need was there to make a prophecy about someone who had alrendy been born before his father became king? Indeed, he does not say: “she conceived”, but: “the virgin shall conceive”, in the style of a prediction.”Cyril of Jerusalem, Catecheses 12, 22; PG 33, 753 B-C.
Gambero, L., 1999. Mary and the Fathers of the Church 1st ed. Translated by Buffer, T., San Francisco: Ignatius Press. p. 135-136