Also the words, Behold, the virgin shall conceive and bear a son were spoken beforehand of Him. For if he of whom Isaiah spake was not about to be born of a virgin, of whom did the Holy Spirit cry aloud, Behold, the Lord Himself shall give a sign. Behold, the virgin shall conceive and shall bear a son? For if he too was about to be born of human intercourse like all other first-born sons, why then did God say He was giving a sign, a thing which is not common to all first-born sons?
But what is really a sign, and what was to become a sure proof to the human race, namely the first-born of all creatures to become incarnate through a virgin’s womb, and really to become a child, this He anticipated by the spirit of the prophets in various ways, as I have related to you, and He made the proclamation beforehand, in order that when it took place it might be known to have taken place by the power and purpose of the maker of the universe; just as Eve came into being from one rib of Adam, and as all other living creatures were begotten by the Word of God in the beginning.
But you dare to mutilate the interpretations which your elders made at the court of Ptolemy king of Egypt, saying that the Scripture has not the meaning they interpret, but, Behold, he says, the young woman will conceive, as though something of importance was being signified, if a woman was to bear after human intercourse, as all young women do save the barren, and these God, if He will, can make bear.
For the mother of Samuel, though she had not borne, yet bare, because it was the will of God, and the wife of Abraham the holy patriarch, and Elizabeth who bare John the Baptist, and certain other women likewise. So that you must not suppose that it is impossible for God to do all whatsoever He will. And especially, when it was prophesied that it should be, do not dare to mutilate or misinterpret the prophecies, for you will injure yourselves alone, but will do no harm to God.