"Now, justification in this life is given to us according to these three things: first by the laver of regeneration by which all sins are forgiven; then, by a struggle with the faults from whose guilt we have been absolved; the third, when our prayer is heard, in which we say: 'Forgive us our debts,' because however bravely we fight against our faults, we are men; but the grace of God so aids as we fight in this corruptible body that there is reason for His hearing us as we ask forgiveness."

Source: 'Contra Julianum' ('Against Julian'). Book by Augustine. Book II, Chapter 8, 22,