The Whole Trinity at the Conception

From this point you may understand the majesty of the Holy Spirit as well. For the Gospel bears witness that when the angel said to the Virgin, “You will bear a son and will call his name Jesus, for he will save his people from their sins,” she answered, “How will this be, since I do not know a man?” And the angel said to her, “The Holy Spirit will come upon you, and the power of the Most High will overshadow you. Therefore the holy one who will be born of you will be called the Son of God.” See here the Trinity working together. The Holy Spirit is spoken of as coming upon the Virgin, and the Power of the Most High as overshadowing her. What is the Power of the Most High but Christ himself, who is the Power of God and the Wisdom of God? And whose Power is it? The Power of the Most High. Here, then, is the Most High, here also is the Power of the Most High, and here also is the Holy Spirit. This is the Trinity, everywhere hidden and everywhere plain, distinct in names and persons, but inseparable in the substance of the Godhead. And although the Son alone is born of the Virgin, yet the Most High is present as well, and the Holy Spirit is present as well, so that both the conceiving and the giving birth of the Virgin might be made holy. [a]