In Genesis 3:15 God says to Satan: “I will put enmity between you and the woman [Mary] and between your offspring and hers [Jesus]. He will strike at your head while you strike at His heal.” The seed of Satan is sin. The seed of the woman is Jesus. Enmity is a complete separation. God applies the term to Mary and Satan as well as to Jesus and sin. If Mary were to sin even once there would be no complete separation between her and Satan. Since the Word of God said there would be enmity between Mary and Satan, the Early Fathers believed it and taught accordingly. Those who say the woman spoken of here was Eve or the Church or even Israel forget that all of those entities either were guilty of sin or were comprised of sinners. Thus there could not be any enmity between them and Satan.
The Odes of Solomon
So the Virgin became a mother with great mercies. And she labored and bore the Son, but without pain, because it did not occur without purpose. And she did not seek a midwife, because he caused her to give life. She bore as a strong man, with will. . . . [Implied as pain during childbirth is the consequence of sin Gen. 3:16] (Odes of Solomon 19 [A.D. 80]).
[Jesus] became man by the Virgin so that the course that was taken by disobedience in the beginning through the agency of the serpent might be also the very course by which it would be put down. Eve, a virgin and undefiled, conceived the word of the serpent and bore disobedience and death. But the Virgin Mary received faith and joy when the angel Gabriel announced to her the glad tidings that the Spirit of the Lord would come upon her and the power of the Most High would overshadow her, for which reason the Holy One being born of her is the Son of God. And she replied, “Be it done unto me according to your word” (Luke 1:38) (Dialogue with Trypho 100 [A.D. 155]).
Consequently, then, Mary the Virgin is found to be obedient, saying, “Behold, 0 Lord, your handmaid; be it done to me according to your word.” Eve . . . who was then still a virgin although she had Adam for a husband — for in paradise they were both naked but were not ashamed; for, having been created only a short time, they had no understanding of the procreation of children . . . having become disobedient [sin], was made the cause of death for herself and for the whole human race; so also Mary, betrothed to a man but nevertheless still a virgin, being obedient [no sin], was made the cause of salvation for herself and for the whole human race. . . . Thus, the knot of Eve’s disobedience was loosed by the obedience of Mary. What the virgin Eve had bound in unbelief, the Virgin Mary loosed through faith (Against Heresies 3:22:24 [A.D. 189]).
This Virgin Mother of the Only-begotten of God is called Mary, worthy of God, immaculate of the immaculate, one of the one (Homily 1 [A.D. 244]).
He [Jesus] was the ark formed of incorruptible wood. For by this is signified that His tabernacle [Mary] was exempt from defilement and corruption (Orat. In Illud, Dominus pascit me, in Gallandi, Bibl. Patrum, II, 496 ante [A.D. 235]).
The Word, then, visited that earth in which He was yet always present; and saw all these evils. He takes a body of our Nature, and that of a spotless Virgin, in whose womb He makes it His own, wherein to reveal Himself, conquer death, and restore life (On the Incarnation of the Word 8 [A.D. 319]).
Ephraim the Syrian
You alone and your Mother are more beautiful than any others, for there is neither blemish in you nor any stains upon your Mother. Who of my children can compare in beauty to these? (Nisibene Hymns 27:8 [A. D. 361]).
Ambrose of Milan
Come, then, and search out your sheep, not through your servants or hired men, but do it yourself. Lift me up bodily and in the flesh, which is fallen in Adam. Lift me up not from Sarah but from Mary, a Virgin not only undefiled but a Virgin whom grace had made inviolate, free of every stain of sin (Commentary on Psalm 118:22-30 [A.D. 387]).
He was conceived by the virgin, who had been first purified by the Spirit in soul and body; for, as it was fitting that childbearing should receive its share of honor, so it was necessary that virginity should receive even greater honor (Sermon 38 [A.D. 390]).
John the Theologian
And from that time forth all knew that the spotless and precious body had been transferred to paradise (The Falling Asleep of Mary [A.D. 400]).