If the Word of God is quick and energising, and the Lord did all that He willed…can He not then make the bread His body and the wine and water His blood?
He said in the beginning, Let the earth bring forth grass, and even until this present day, when the rain comes it brings forth its proper fruits, urged on and strengthened by the divine command.
God said, This is My body, and This is My blood, and this do ye in remembrance of Me.
And so it is at His omnipotent command until He come…, and the overshadowing power of the Holy Spirit becomes through the invocation the rain to this new tillage.
For just as God made all that He made by the Energy of the Holy Spirit, so also now the Energy of the Spirit performs those things that are supernatural and which it is not possible to comprehend unless by faith alone.
How shall this be, said the holy Virgin, seeing I know not a man? And the archangel Gabriel answered her: The Holy Spirit shall come upon thee, and the power of the Highest shall overshadow thee.
And now you ask, how the bread became Christ’s body and the wine and water Christ’s blood. And I say unto thee, “The Holy Spirit is present and does those things which surpass reason and thought.”
[…] The body which is born of the holy Virgin is in truth body united with divinity, not that the body which was received up into the heavens descends, but that the bread itself and the wine are changed into God’s body and blood.
But if you enquire how this happens, it is enough for you to learn that it was through the Holy Spirit, just as the Lord took on Himself flesh that subsisted in Him and was born of the holy Mother of God through the Spirit.
And we know nothing further save that the Word of God is true and energises and is omnipotent, but the manner of this cannot be searched out.
But one can put it well thus, that just as in nature the bread by the eating and the wine and the water by the drinking are changed into the body and blood of the eater and drinker, and do not become a different body from the former one, so the bread of the table and the wine and water are supernaturally changed by the invocation and presence of the Holy Spirit into the body and blood of Christ, and are not two but one and the same.
John Damascene (c.675-749): De Fide Orthodoxa 4, 13.