It was necessary for us to have a new root for our race, a new Adam, not just one Who would be sinless and invincible, but one Who also would be
able to forgive sins and set free from punishment those subject to it. And not only would He have life in Himself, but also the capacity to restore to life,
...Except for God, there is no one who is without sin, or life-creating, or able to remit sin. Therefore, the new Adam must be not only Man, but also God.
...It was a deed of perfect justice that our nature, which was voluntarily enslaved and struck down, should again enter the struggle for victory and cast off its voluntary enslavement. Therefore, God deigned to receive our nature from us, hypostatically uniting with it in a marvellous way. But it was impossible to unite that Most High Nature,Whose purity is incomprehensible for human reason, to a sinful nature before it had been purified. Therefore, for the conception and birth of the Bestower of purity, a perfectly spotless and Most Pure Virgin was required.
...In this manner, the choice of the future Mother of God, beginning with the very sons of Adam and proceeding through all the generations of time, through the Providence of God, passes to the Prophet-king David and the successors of his kingdom and lineage. When the chosen time had come, then from the house and posterity of David, Joachim and Anna are chosen by God.