Glossa Ordinaria
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.
(ap. Anselm.) Or, he says, all this was done, meaning, the Virgin was betrothed, she was kept chaste, she was found with child, the revelation was made by the Angel, that it might be fulfilled which was spoken. For that the Virgin should conceive and should bring forth would never have been fulfilled, had she not been espoused that she should not be stoned; and had not her secret been disclosed by the Angel, and so Joseph taken her unto him, that she was not dismissed to disgrace and to perish by stoning. So had she perished before the birth, that prophecy would have been made void which says, She shall bring forth a Son. (Isa. 7:14.)