Nicene and Post-Nicene Fathers, Vol. V:
A Treatise on the Merits and Forgiveness...: Chapter 55

Chapter 55.—To Recover the Righteousness Which Had Been Lost by Sin, Man Has to Struggle, with Abundant Labour and Sorrow.

The flesh which was originally created was not that sinful flesh in which man refused to maintain his righteousness amidst the delights of Paradise, wherefore God determined that sinful flesh should propagate itself after it had sinned, and struggle for the recovery of holiness, in many toils and troubles. Therefore, after Adam was driven out of Paradise, he had to dwell over against Eden,—that is, over against the garden of delights,—to indicate that it is by labours and sorrows, which are the very contraries of delights, that sinful flesh had to be educated, after it had failed amidst its first pleasures to maintain its holiness, previous to its becoming sinful flesh. As therefore our first parents, by their subsequent return to righteous living, by which they are supposed to have been released from the worst penalty of their sentence through the blood of the Lord, were still not deemed worthy to be recalled to Paradise during their life on earth, so in like manner our sinful flesh, even if a man lead a righteous life in it after the remission of his sins, does not deserve to be immediately exempted from that death which it has derived from its propagation of sin. 639

Footnotes

See also his treatise, De Naturâ et Gratiâ, ch. xxiii.