“This seed of the woman therefore, because he is to crush the devil’s power, that is, sin and death, must not be an ordinary man, since all men have been brought under the devil through sin and death. So he must certainly be without sin. Now human nature does not produce such seed or fruit, as has been said, for with their sin they are all under the devil. How, then, can this be? The seed must be the natural child of a woman; otherwise, it could not be or be called the seed of the woman. On the other hand, as has been pointed out, human nature and birth does not produce such seed. Therefore, the solution must ultimately be that this seed is a true natural son of the woman; derived from the woman, however, not in the normal way but through a special act of God, in order that the Scripture might stand, that he is the seed only of a woman and not of a man. For the text [Gen. 3:15] clearly states that he will be the seed of woman.
This is thus the first passage in which the mother of this child is described as a virgin. She is his true natural mother; yet she is to conceive and bear supernaturally, by God, without a man, in order that her child may be a distinctive man, without sin, yet having ordinary flesh and blood like other men. This could not have been the case had he been begotten by a man like other men because the flesh is consumed and corrupted by evil lust, so that its natural act of procreation cannot occur without sin. Whatever conceives and bears through an act of the flesh produces also a carnal and sinful fruit. This is why St. Paul says in Ephesians 1 [2:3] that we are all by nature children of wrath” (Luther’s Works, v.45, p.202).