The grace of God through Jesus Christ our Lord must be understood as follows: grace is the only thing that delivers human beings from evil; without it, they do absolutely nothing good, whether in thought, or in will and emotion, or in action. Grace not only makes known to people what they ought to do, but also enables them to perform with love the duty that they know.
The apostle Paul certainly asked God to inspire the Corinthians with this good will and action when he said, ‘Now we pray to God that you do no evil, not that we should appear to be approved, but that you should do what is good’ (2 Cor.13:7). Who can hear this and not wake up and confess that the Lord God is the One Who turns us away from evil so that we do good? For the apostle does not say, ‘We admonish, we teach, we exhort, we rebuke.’ He says, ‘We pray to God that you do no evil, but that you should do what is good.’ Of course, he was also in the habit of speaking to them, and doing all those things which I have mentioned — he admonished, he taught, he exhorted, he rebuked. But he knew that all these things which he was openly doing in the way of planting and watering were of no avail, unless He Who secretly gives the increase answered his prayer on the Corinthians’ behalf. For as the same teacher of the Gentiles says, ‘Neither he who plants is anything, nor he who waters, but God Who gives the increase’ (1 Cor.3:7).
Augustine On Rebuke and Grace, 3