Augustine of Hippo
Catena Aurea · Matthäusevangelium 1
Now the birth of Jesus Christ was on this wise: When as His mother Mary was espoused to Joseph, before they came together, she was found with child of the Holy Ghost.
(Enchir c. 40.) Furthermore, this manner in which Christ was born of the Holy Spirit suggests to us the grace of God, by which man without any previous merits, in the very beginning of his nature, was united with the Word of God into so great unity of person, that he was also made son of God. (c. 38.). But inasmuch as the whole Trinity wrought to make this creature which was conceived of the Virgin, though pertaining only to the person of the Son, (for the works of the Trinity are indivisible,) why is the Holy Spirit only named in this work? Must we always, when one of the Three is named in any work, understand that the whole Trinity worked in that?