This is from the Athanasian Creed.
People whose concept of divinity is a concept of three persons cannot have a concept of one God. If they say “one” with their mouth, they still think “three.” However, people whose concept of divinity is a concept of three aspects in one person can have a concept of one God. They can say “one God,” and they can think “one God” as well.
Our concept of God is a concept of three aspects in one person when we think that the Father is in the Lord and that the Holy Spirit emanates from the Lord. In this case all three aspects are in the Lord: divinity itself, which is called the Father; the divine-human nature, which is the Son; and divinity emanating, which is the Holy Spirit.
Since all divinity is in the Lord, he has all power in heaven and on earth. This he himself tells us in John:
“The Father has given all things into the hand of the Son” (John 3:35);
“The Father has given the Son power over all flesh” (John 17:2);
“All things have been delivered to me by the Father” (Matthew 11:27);
“All power has been given to me in heaven and on earth” (Matthew 28:18).
Divinity is that kind of power.
People who suppose the Lord’s human nature to be just like the human nature of anyone else are not taking into consideration that he was conceived by the Divine, nor are they pondering the fact that the body is for everyone an image of the soul. Nor are they considering that he was resurrected with his whole body, nor the way he appeared when he was transfigured, when his face shone like the sun.
Nor do they think about what the Lord said about believing in him, about his being one with the Father, about his glorification, and about his power over heaven and earth—that these are divine attributes and yet they are said of his human nature.
Nor do they bear in mind that the Lord is omnipresent even with respect to his human nature (Matthew 28:20), though this is the basis of belief in his omnipresence in the Holy Supper—omnipresence is a divine trait.
Perhaps people do not even consider that the divinity called the Holy Spirit emanates from the Lord’s human nature, when in fact it does emanate from his glorified human nature; for it says,
“There was not the Holy Spirit yet because Jesus was not yet glorified” (John 7:39).
The Lord came into the world to save the human race, which otherwise would have suffered eternal death. He saved it by gaining control over the hells, which were assaulting everyone who entered this world and everyone who left it. He also saved the human race by glorifying his own human nature, because this gave him the power to keep the hells under his control forever.
His gaining control over the hells and the simultaneous glorification of his human nature were effected by allowing the human nature that he received from his mother to undergo spiritual crises and by continuous victories in those crises. His suffering on the cross was his last spiritual crisis; in it he made his victory complete.
from New Jerusalem, Sections 289-293