[...] Indeed, our reconciliation to God could not have been accomplished through Christ who saves us except by communion in the Spirit and sanctification.
For that which knits us together, and, as it were, unites us with God, is the Holy Spirit.
If we receive the Spirit, we are proved sharers and partakers in the divine nature, and we admit the Father Himself into our hearts, through the Son and in the Son.
Further, the wise John writes for us concerning Him: Hereby know we that we abide in Him, and He in us, because He has given us of His Spirit.
And what does Paul also say? And because ye are sons, God sent forth the Spirit of His Son into your hearts, crying, Abba, Father.
For if we had chanced to remain without partaking of the Spirit, we could never at all have known that God was in us.
And, if we had not been enriched with the Spirit that puts us into the rank of sons, we should never have been at all the sons of God.
How, then, should we…have been shown to be partakers in divine nature unless God had been in us, and unless we been joined to Him through having been called to communion with the Spirit?
But now are we both partakers and sharers in the divine substance that transcends the universe, and are become temples of God.
For the Only-begotten sanctified Himself for our sins. That is, offered Himself up, and brought Himself as a holy sacrifice for a sweet-smelling savour to God the Father.
He did this in order that, while He as God came between and hedged off and built a wall of partition between human nature and sin.
This was so that nothing might hinder our being able to have access to God, and to have close fellowship with Him through communion – that is, with the Holy Spirit moulding us anew to righteousness and sanctification and the original likeness of man.
For if sin sunders and dissevers man from God, surely righteousness will be a bond of union, and will somehow set us by the side of God Himself, with nothing to part us.
We have been justified through faith in Christ, Who was delivered up for our trespasses, according to the Scripture, and was raised for our justification.
For in Him, as in the first-fruits of the race, the nature of man was wholly reformed into newness of life, and ascending, as it were, to its own first beginning, was moulded anew into sanctification.
Cyril of Alexandria (c. 376-444): Commentary on St John’s Gospel, book 11, c.10 [on John 17:18-19].