Isaiah 66:7

(V. 7) Before she was in labor, she gave birth; before her pain came, she delivered a male child. Who has heard of such a thing? Who has seen such things? Can a land be born in one day? Can a nation be brought forth all at once? For as soon as Zion was in labor, she gave birth to her sons. Shall I bring to the point of birth and not give delivery? says the Lord. Or shall I who gives delivery shut the womb? says your God.

Now that that parturition was polluted, and stood not in need of expiatory victims, Isaiah is our witness, who proclaims distinctly to the whole earth under the sun: "Before she travailed," he says, "she brought forth before her pains came, she escaped, and brought forth a man-child." Who hath heard such a thing? Who hath seen such things? The most holy virgin mother, therefore, escaped entirely the manner of women even before she brought forth: doubtless, in order that the Holy Spirit, betrothing her unto Himself, and sanctifying her, she might conceive without intercourse with man. She hath brought forth her first-born Son, even the only-begotten Son of God, Him, I say, who in the heavens above shone forth as the only-begotten, without mother, from out His Father's substance, and preserved the virginity of His natural unity undivided and inseparable; and who on earth, in the virgin's nuptial chamber, joined to Himself the nature of Adam, like a bridegroom, by an inalienable union, and preserved His mother's purity uncorrupt and uninjured—Him, in short, who in heaven was begotten without corruption, and on earth brought forth in a manner quite unspeakable.

Again Isaiah teaches that Jerusalem will not be destroyed root, branch and all. For when he foretold the complete captivity of Jerusalem, he mentioned those chosen to survive. For a not insignificant number will be saved, obviously through faith in Christ—and he wants to make this clear. But the Jews were enraged with him and killed the prince of life. But when he rose again, trampling on death, he returned to his God and Father in heaven. In the meantime, the divine apostles proclaimed him to all, and they called even those who had been enraged with him to repentance and to salvation through faith and the forgiveness of sins through baptism.

Second, he describes the promise as to abundance of goods. And first, as to the reuniting of the people, setting out the promise, before she was in labor, she brought forth; that is, the children of Jerusalem will be gathered to her suddenly and at …

Now when the fullness of time came, an angel of the Lord was sent to [Mary] with the good news of her conception of the Lord. And thus she conceived the Son of God, the subsistent power of the Father, "not of the will of the flesh or of the will of man"—that is to say, not of carnal conjunction and seed—but of the good pleasure of the Father and the cooperation of the Holy Spirit. To the Creator she gave that he might be created, to the Fashioner that he might be fashioned, and to the Son of God and God that he might from her innocent and undefiled flesh and blood put on flesh and become man. And thus she paid the debt for the first mother. For as Eve was formed from Adam without carnal conjunction, so did this one bring forth the new Adam in accordance with the law of gestation but surpassing the nature of generation. Thus, he who is without a mother begotten of a father was without a father born of a woman. And because it was of a woman it was in accordance with the law of gestation; while, because it was without father, it surpassed the nature of generation. And because it was at the normal time, for having completed the nine-month period he was born at the beginning of the tenth, it was in accordance with the law of gestation, while because it was without pain it surpassed the established order of birth—for where pleasure had not preceded, pain did not follow, as the prophet said, "Before she was in labor, she brought forth," and again, "before her time came to be delivered she brought forth a man child."And so the Son of God became incarnate and was born of her. It was not as God-bearing man that he was born of her but as God incarnate; not as a prophet anointed through the operation of the one anointing but as one anointed with the entire presence of the one anointing—so that the one anointing became man and the one anointed became God.