“Now there was, no doubt, a decided merit in the Apostle Paul, but it was an evil one, while he persecuted the Church, and he says of it: “I am not meet to be called an apostle, because I persecuted the Church of God.” 1 Corinthians 15:9 And it was while he had this evil merit that a good one was rendered to him instead of the evil; and, therefore, he went on at once to say, “But by the grace of God I am what I am.” 1 Corinthians 15:10 Then, in order to exhibit also his free will, he added in the next clause, “And His grace within me was not in vain, but I have laboured more abundantly than they all.”
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Augustine of Hippo,
On Grace and Free Will