For it is God who works in you both to will and to do of his good pleasure.
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Augustine of Hippo
AD 430
We should not suppose, because he said, “For it is God that works in you both the willing and the doing,” that he has taken away free will. For if that were so he would not have said above “Work out your own salvation with fear and trembling.” For when he bids them work, it is agreed that they have free will. But they are to work with fear and trembling so that they will not, by attributing the good working to themselves, be elated by the good works as though they were their own.
It is certain that when we do a deed the deed is ours; but he is the one who makes us do the deed by giving us strength fully sufficient to carry out our will.
It is not in God’s power that anyone should be forced against his will to do evil or good but that he should go to the bad, according to his own deserts, when God abandons him. For a person is not good if he does not will it, but the grace of God assists him even in willing. It is not without cause that it is written, “God is the one who works in you to will and do, of his own good will.”
It is God who worketh in you both to will and to accomplish. We can neither have a will, nor begin, nor fulfil any thing of ourselves, in order to a reward in heaven. (Witham)
Our free-will is not taken away, or we should not be commanded to work; but it is added, with fear and trembling, says St. Augustine, that we might not be proud of our good works. (De grat. et de lib. ab. chap. ix.)
If you have the will, then he works the willing. Do not be afraid or weary. He gives us both zeal and performance. For when we will, he will henceforth augment our willing. .
And when he says “with fear and trembling” see how he assuages the pain of it. For what does he say? “It is God who works in you.” “Do not be afraid,” he says, “because I said ‘with fear and trembling.’ I did not say it to make you give up, thinking virtue impossible of attainment, but so that you may carry on, so that you may not collapse.” .