Let them then, who of their folly have not yet admitted the faith in Christ, hear, Except ye eat the Flesh of the Son of Man and drink His Blood, ye have no life in you.
For wholly destitute of all share and taste of that life which is in sanctification and bliss, do they abide who do not through the mystical Blessing [i.e. the Eucharist] receive Jesus.
For He is Life by nature, inasmuch as He was begotten of a living Father: no less quickening is His holy Body also, being in a manner gathered and ineffably united with the all-quickening Word.
Wherefore His Body is accounted His, and is conceived of as one with Him. For, since the Incarnation, it is inseparable.
The Word which came from God the Father, and the temple from the Virgin, are not indeed the same in nature (for the Body is not consubstantial with the Word from God), yet are they One by that coming-together and ineffable concurrence.
And since the Flesh of the Saviour hath become life-giving (as being united to that which is by nature Life, the Word from God), when we taste It, then have we life in ourselves, we too united to It, as It to the indwelling Word.
For this cause also, when He raised the dead, the Saviour is found to have operated, not by word only, or God-befitting commands, but He laid a stress on employing His Holy Flesh as a sort of co-operator unto this, that He might shew that It had the power to give life, and was already made one with Him.
For it was in truth His Own Body, and not another’s. And verily when He was raising the little daughter of the chief of the Synagogue saying, Maid, arise, He laid hold of her hand, as it is written, giving life, as God, by His all-powerful command, and again, giving life through the touch of His holy Flesh, He shews that there was one kindred operation through both.
Yea and when He went into the city called Nain, and one was being carried out dead, the only son of his mother, again He touched the bier, saying, Young man, to thee I say, Arise.
And not only to His Word gives He power to give life to the dead, but that He might shew that His own Body was life-giving (as I have said already), He touches the dead, thereby also infusing life into those already decayed.
And if by the touch alone of His holy Flesh, He gives life to that which is decayed, how shall we not profit yet more richly by the life-giving Blessing when we also taste It? For It will surely transform into Its own good, i. e., immortality, those who partake of It.
Cyril of Alexandria (c. 376-444): Commentary on St John’s Gospel, book 4, c.12 [on John 6:53].