Psalms 59:9

In order not to falter in good works, we ought always to rely for support on the help of the one who says, "For without me you can do nothing." Hence in order to express the fact that the start of faith and good action is given to us by the Lord, the psalmist properly says, "My God, his mercy goes before me." Again, in order to teach that the good things we do must be accomplished with his assistance, he says, "And your mercy follows after me all the days of my life." In order to show that the prize of eternal life rendered for good works is bestowed on us freely, he says, "Who crowns you in compassion and mercy." He crowns us indeed in mercy and compassion when he repays us with the reward of heavenly blessedness for the good works that he himself has mercifully granted us to carry out.

Therefore, it is good for a person to say truthfully and with the full strength of his free will, "I will provide you with my strength," because the man who thought he could keep it without the help of him who gave it went abroad into a far country and wasted his substance, living riotously. But, worn down by the wretchedness of a harsh slavery, he returned to himself and said, "I will arise and go to my father." But how could he have had this good thought if the most merciful Father had not whispered it to him in secret? It was because he understood this that the minister of the New Testament said, "Not that we are sufficient to think anything of ourselves as of ourselves, but our sufficiency is from God." Consequently, when the psalmist also had said, "I will provide you with my strength," lest he should attribute to himself the fact that he was keeping it, and as if he recalled to mind that "except the Lord keep the city, they watch in vain that keep it," and that "he shall neither slumber nor sleep that keeps Israel," he added the reason of his being able to keep it, or, rather, the guard by whom it is kept and said, "For you, O God, are my protector."

There remains the Pelagians' second act of wickedness, because they posit free will to such a degree in human strength that they think that they by themselves, apart from the grace of God, can conceive of some good or do it. But if this were the case, why would the prophet say, "O my God, his mercy will precede me"? When you hear that you were preceded by the mercy of the Lord, one is given to understand that nothing of yours preceded God's mercy. In another psalm he also says, "Unless the Lord builds the house, they labor in vain who built it." Again he says, "The steps of a person are directed by the Lord and he delights exceedingly in his way." In another place the psalmist also attests, "The Lord raises up those who have been broken; the Lord loosens those who have been shackled; the Lord gives light to the blind." When you hear that the Lord goes before, builds, directs and raises up, unbinds and illumines without any preceeding merits, what of your own do you recognize that you have begun except only that by which you are rightly damned for your haughtiness?… But you interpret these words and others similar to them with the most evil intention, namely, in order that you may believe that people take the beginning of their good will from their own powers and afterwards receive the help of grace, so that (it is wrong for this even to be uttered!) we are the cause of his kindness rather than he being the cause of his own kindness.