God's Grace Works in Us Sovereignly to Produce a Godly Will
"Some might interpret ˜It is not of him who wills, nor of him who runs, but of God Who shows mercy" (Rom.9:16), in this sense, that salvation comes from both, that is, both from the human will and from the mercy of God. In that case, we must understand the saying, "It is not of him who wills, nor of him who runs, but of God Who shows mercy," as if it meant that the human will alone is not sufficient, unless the mercy of God goes with it. But then it would follow that the mercy of God alone is not sufficient, unless the human will goes with it! Therefore, if we may rightly say, ˜it is not of man who wills, but of God Who shows mercy," because the human will by itself is not enough, why may we not also rightly put it the other way round: ˜It is not of God Who shows mercy, but of man who wills," because the mercy of God by itself is not sufficient? Surely, no Christian will dare to say this, "It is not of God Who shows mercy, but of man who wills," in case he openly contradicts the apostle!
So it follows that the true interpretation of the saying, "It is not of him who wills, nor of him who runs, but of God Who shows mercy," is that the entire work belongs to God, Who both makes the human will righteous, and prepares it in this way for His assistance, and then assists it when it is prepared. For human righteousness of will precedes many of God's gifts, but not all of them; and it must itself be included among those gifts which it does not precede. We read in Holy Scripture, both that God's mercy ˜shall meet me" (Ps.59:10), and that His mercy "shall follow me" (Ps.23:6). Mercy goes before the unwilling person to make him willing; it follows the willing person to make his will effective. Why are we taught to pray for our enemies, who are plainly unwilling to lead a holy life, unless that God may produce willingness in them? And why are we ourselves taught to ask in order that may receive, unless that He who has created in us the wish, may Himself satisfy the wish? We pray, then, for our enemies, that the mercy of God may go before them, as it has gone before us; and we pray for ourselves that His mercy may follow us.
From Enchiridion, by St. Augustine