8th Century
St. John Damascene
Late Patristic
St. John Damascene (c. 675 – 749), Monk, priest, and Doctor of the Church. Wikipedia
"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. "
On the Orthodox Faith IV.13
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Why this quote matters
Change occurs by the Holy Spirit; mystery beyond explanation.
Source citation: trans. S. D. F. Salmond, NPNF ser. 2, vol. 9 (1899), p. 83.