On The Holy Trinity by St. Augustine
Chapter 17.--How the Image of God in the Mind is Renewed Until the Likeness of God is Perfected in It in Blessedness.
23. Certainly this renewal does not take place in the single moment of conversion itself, as that renewal in baptism takes place in a single moment by the remission of all sins; for not one, be it ever so small, remains unremitted. But as it is one thing to be free from fever, and another to grow strong again from the infirmity which the fever produced; and one thing again to pluck out of the body a weapon thrust into it, and another to heal the wound thereby made by a prosperous cure; so the first cure is to remove the cause of infirmity, and this is wrought by the forgiving of all sins; but the second cure is to heal the infirmity itself, and this takes place gradually by making progress in the renewal of that image: which two things are plainly shown in the Psalm, where we read, |Who forgiveth all thine iniquities,| which takes place in baptism; and then follows, |and healeth all thine infirmities;| and this takes place by daily additions, while this image is being renewed. And the apostle has spoken of this most expressly, saying, |And though our outward man perish, yet the inner man is renewed day by day.| And |it is renewed in the knowledge of God, i.e. in righteousness and true holiness,| according to the testimonies of the apostle cited a little before. He, then, who is day by day renewed by making progress in the knowledge of God, and in righteousness and true holiness, transfers his love from things temporal to things eternal, from things visible to things intelligible, from things carnal to things spiritual; and diligently perseveres in bridling and lessening his desire for the former, and in binding himself by love to the latter. And he does this in proportion as he is helped by God. For it is the sentence of God Himself, |Without me ye can do nothing.| And when the last day of life shall have found any one holding fast faith in the Mediator in such progress and growth as this, he will be welcomed by the holy angels, to be led to God, whom he has worshipped, and to be made perfect by Him; and so will receive in the end of the world an incorruptible body, in order not to punishment, but to glory. For the likeness of God will then be perfected in this image, when the sight of God shall be perfected. And of this the Apostle Paul speaks: |Now we see through a glass, in an enigma, but then face to face.| And again: |But we with open face, beholding as in a glass the glory of the Lord, are changed into the same image, from glory to glory, even as by the spirit of the Lord.| And this is what happens from day to day in those that make good progress.