John Chrysostom
Catena Aurea · Matthäusevangelium 1
Now all this was done, that it might be fulfilled which was spoken of the Lord by the prophet, saying, Behold, a Virgin shall be with child, and shall bring forth a Son, and they shall call His Name Emmanuel, which being interpreted is, God with us. Here we must enquire why he should say all this was done, when above he has only related the conception. It should be known that he says this to shew, that in the presence of God all this was done before it was done among men. Or he says, all this was done, because he is relating past events; for when he wrote, it was all done.
Otherwise; the Angel seeing the depths of the Divine mercy, the laws of nature broken through and reconciliation made, He who was above all made lower than all; all these wonders, all this he comprises in that one saying, Now all this hath happened; as though he had said, Do not suppose that this is newly devised of God, it was determined of old. And he rightly cites the Prophet not to the Virgin, who as a maiden was untaught in such things, but to Joseph, as to one much versed in the Prophets. And at first he had spoken of Mary as thy wife, but now in the words of the Prophet he brings in the word “Virgin,” that he might hear this from the Prophet, as a thing long before determined. Therefore to confirm what he had said, he introduces Isaiah, or rather God; for he does not say, Which was spoken by Isaiah, but, Which was spoken of the Lord by the Prophet.