Blessed Theophylact of Ochrid: On the nature of the Holy Eucharist

John 6:56-58: "He that eateth My flesh, and drinketh My blood, dwelleth in Me, and I in him. As the living Father hath sent Me, and I live by the Father: so he that eateth Me, even he shall live by Me. This is that bread which came down from heaven: not as your fathers did eat manna in the wilderness, and are dead: he that eateth of this bread shall live for ever." Here we learn more about the sacrament of Communion. He who eats and drinks of the Lord's flesh and blood dwells in the Lord Himself, and the Lord in him. A strange and marvelous intermingling occurs, such that God is in us, and we in God. Is not this frightful to hear? We do not consume God in His essence. He is intangible and bodiless, and we cannot take hold of Him with our teeth any more than we can apprehend Him with eyes. Neither do we consume the flesh of a mere man, which would bring us no benefit. But since God has united flesh to Himself by an ineffable union, even His flesh becomes life-creating. But His flesh has not changed into the nature of God. Far from it! Just as red-hot iron manifests the energy of fire while remaining iron, so Christ's flesh is life-creating - imparting the divine energy of God the Word - without ceasing to be human.
+Blessed Theophylact of Ochrid¹, from The Explanation of the Holy Gospel according to John, chapter 6.
¹Theophylact is commemorated as a saint by the Serbian Church. Here we use the more common appellation "blessed".