6 You will, indeed, take the better course (as I earnestly request you), if you will not refuse to send to me the very person by whom they say they have been disturbed. For either he does not understand my book, or else, perhaps, he is himself misunderstood, when he endeavours to solve and explain a question which is a very difficult one, and intelligible to few. For it is none other than the question of God's grace which has caused persons of no understanding to think that the Apostle Paul prescribes it to us as a rule, "Let us do evil that good may come." It is in reference to these that the Apostle Peter writes in his second Epistle; "Wherefore, beloved, seeing that you look for such things, be diligent, that you may be found of Him in peace, without spot and blameless and account that the long-suffering of our Lord is salvation; even as our beloved brother Paul also, according to the wisdom given unto him, has written unto you; as also in all his epistles, speaking in them of these things: in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other Scriptures, unto their own destruction."
Source: Letters (New Advent)