This is from Anselm's Cur Deus homo? Chapter 8
It now remains to inquire whence and how God shall assume human nature. For he will either take it from Adam, or else he will make a new man, as he made Adam originally. But, if he makes a new man, not of Adam’s race, then this man will not belong to the human family, which descended from Adam, and therefore ought not to make atonement for it, because he never belonged to it. For, as it is right for man to make atonement for the sin of man, it is also necessary that he who makes the atonement should be the very being who has sinned, or else one of the same race. Otherwise, neither Adam nor his race would make satisfaction for themselves. Therefore, as through Adam and Eve sin was propagated among all men, so none but themselves, or one born of them, ought to make atonement for the sin of men. And, since they cannot, one born of them must fulfil this work. Moreover, as Adam and his whole race, had he not sinned, would have stood firm without the support of any other being, so, after the fall, the same race must rise and be exalted by means of itself. For, whoever restores the race to its place, it will certainly stand by that being who has made this restoration. Also, when God created human nature in Adam alone, and would only make woman out of man, that by the union of both sexes there might be increase, in this he showed plainly that he wished to produce all that he intended with regard to human 248 nature from man alone. Wherefore, if the race of Adam be reinstated by any being not of the same race, it will not be restored to that dignity which it would have had, had not Adam sinned, and so will not be completely restored; and, besides, God will seem to have failed of his purpose, both which suppositions are incongruous: It is, therefore, necessary that the man by whom Adam’s race shall be restored be taken from Adam. ...
Let us now examine the question, whether the human nature taken by God must be produced from a father and mother, as other men are, or from man alone, or from woman alone. For, in whichever of these three modes it be, it will be produced from Adam and Eve, for from these two is every person of either sex descended. And of these three modes, no one is easier for God than another, that it should be selected on this account.
... It is no great toil to show that that man will be brought into existence in a nobler and purer manner, if produced from man alone, or woman alone, than if springing from the union of both, as do all other men.
... Therefore must he be taken either from man alone, or woman alone.
... In four ways can God create man, viz., either of man and woman, in the common way; or neither of man nor woman, as he created Adam; or of man without woman, as he made Eve; or of woman without man, which thus far he has never done. Wherefore, in order to show that this last mode also under his power, and was reserved for this very purpose, what more fitting than that he should take that man whose origin we are seeking from a woman without a man? Now whether it be more worthy that he be born of a virgin, or one not a virgin, we need not discuss, but must affirm, beyond all doubt, that the God-man should be born of a virgin.
... as man’s sin and the cause of our condemnation sprung from a woman, so the cure of sin and the source of our salvation should also be found in a woman. And that women may not despair of attaining the inheritance of the blessed, because that so dire an evil arose from woman, it is proper that from woman also so great a blessing should arise, that their hopes may be revived. Take also this view. If it was a virgin which brought all evil upon the race, it is much more appropriate that a virgin should be the occasion of all good. And this also. If woman, whom God made from man alone, was made of a virgin (de virgine), it is peculiarly fitting for that man also, who shall spring from a woman, to be born of a woman without man. Of the pictures which can be superadded to this, showing that the God-man ought to be born of a virgin, we will say nothing. These are sufficient.