4 C. Talk as you like, argue as you please, you will never wrest from me free will, which God bestowed once for all, nor will you be able to deprive me of what God has given, the ability if I have the will.
A. By way of example let us take one proof: “I have found David, the Son of Jesse, a man after My own heart, who shall do all My will.” There is no doubt that David was a holy man, and yet he who was chosen that he might do all God's will is blamed for certain actions. Of course it was possible for him who was chosen for the purpose to do all God's will. Nor is God to blame Who beforehand spoke of his doing all His will as commanded, but blame does attach to him who did not what was foretold. For God did not say that He had found a man who would unfailingly do His bidding and fulfil His will, but only one who would do all His will. And we, too, say that a man can avoid sinning, if he chooses, according to his local and temporal circumstances and physical weakness, so long as his mind is set upon righteousness and the string is well stretched upon the lyre. But if a man grow a little remiss it is with him as with the boatman pulling against the stream, who finds that, if he slackens but for a moment, the craft glides back and he is carried by the flowing waters whither he would not. Such is the state of man; if we are a little careless we learn our weakness, and find that our power is limited. Do you suppose that the Apostle Paul, when he wrote “the coat (or cloak) that I left at Troas with Carpus, bring when you come, and the books, especially the parchments,” was thinking of heavenly mysteries, and not of those things which are required for daily life and to satisfy our bodily necessities? Find me a man who is never hungry, thirsty, or cold, who knows nothing of pain, or fever, or the torture of strangury, and I will grant you that a man can think of nothing but virtue. When the Apostle was struck by the servant, he delivered himself thus against the High Priest who commanded the blow to be given: “God shall strike you, thou whited wall.” We miss the patience of the Saviour Who was led as a lamb to the slaughter, and opened not His mouth, but mercifully said to the smiter, “If I have spoken evil, bear witness of the evil; but if well, why do you smite Me?” We do not disparage the Apostle, but declare the glory of God Who suffered in the flesh and overcame the evil inflicted on the flesh and the weakness of the flesh— to say nothing of what the Apostle says elsewhere: “Alexander, the coppersmith, did me much evil; the Lord, the righteous Judge, will recompense him in that day.”
Source: Against the Pelagians (New Advent)