“Receive ye the Holy Ghost: whosesoever sins ye forgive, they are forgiven unto them; whosesoever sins ye retain, they are retained” (John 20:22-23).
He proclaimed that He would send down to us from heaven the Comforter, when He was ascended to God the Father.
And this, indeed, He did, when He had gone away to the Father, and vouchsafed to shed forth the Spirit abundantly upon all who were willing to receive it.
For any man could receive it, through faith, that is, and Holy Baptism.
And then was fulfilled that which was spoken by the voice of the Prophet: I will pour out of My Spirit upon all flesh.
[…] For God the Father, at the beginning, by His own Word, took of the dust of the ground, as is written, and fashioned the animal, that is man, and endowed him with a soul, according to His Will.
And He illuminated him with a share of His own Spirit; for He breathed into his nostrils the breath of life, as is written.
And when it came to pass that through disobedience man fell under the power of death, and lost his ancient honour, God the Father built him up and restored him to newness of life, through the Son, as at the beginning.
And how did the Son restore him? By the death of His own Flesh He slew death, and brought the race of man back again into incorruption; for Christ rose again for us.
In order, then, that we might learn that He it was Who at the beginning created our nature, and sealed us with the Holy Spirit, our Saviour again grants the Spirit, through the outward sign of His Breath, to the holy disciples, as being the firstfruits of renewed nature.
For Moses writes concerning our creation of old, that God breathed into man’s nostrils the breath of life.
As, then, at the beginning, man was formed and came into being, so likewise is he renewed.
And as he was then formed in the Image of his Creator, so likewise now, by participation in the Spirit, is he transformed into the Likeness of his Maker.
For that the Spirit impresses the Saviour’s Image on the hearts of those who receive Him surely does not admit of question.
For Paul plainly exhorts those who had fallen through weakness into observance of the Law, in the words: My little children, of whom I am again in travail until Christ be formed in you.
For he says that Christ will not be formed in them save by partaking of the Holy Spirit, and living according to the law of the Gospel.
Therefore, as in the firstfruits of creation, which is made regenerate into incorruption and glory and into the Image of God, Christ establishes anew His own Spirit in His disciples.
Cyril of Alexandria (c. 376-444): Commentary on John, Book 12 (on John 20:22-23) [slightly adapted].