The absence of sin in Mary meant holiness—a holiness in which she steadily grew. When the time came for the angel of God to visit her, he could salute her as “full of grace” and “blessed among women.”

Never before did a messenger from God address a human being in such language. There must have been a reason.

There are two important points that must be kept in mind in finding that reason. The first is that God does nothing by chance or on the spur of the moment. The Eternal God simply does not act that way. What he does in the world, he has planned from the beginning of time. He did not just happen to send an angel to a small Judean town to a nice Jewish girl whom he selected to be the mother of the Messias after a quick omniscient glance over all the others and a quick decision that she was to be the one. She was in his mind from the beginning. When she came into existence, it was to be the mother of God.

The second point is that when God gives anyone a work to do, he gives the wherewithal to do it right. St. Paul, for example, said, “God has made us fit ministers of the new covenant”

(2 Cor 3:6). In other words, by his grace, he has made us fit to fulfill that to which he has called us. God, then, who chose Mary to be the mother of God, gave her grace, blessedness, and holiness that made her worthy of that dignity. She was fit to be the mother of God and to receive God himself into her bosom. In Mary there was no shame of sin to reflect on her child. The flesh which the Holy One took from her as his mother was the flesh of one who had never been – in any sense – a sinner.

Early Christian Reverence which the above was taken from: Pertinent passages from their works have been translated into English and collected into volumes such as the one entitled, "The Blessed Virgin in the Fathers of the First Six Centuries by Thomas Livius", published by Burns & Oates.