Tertullian

“ It is true that he tells us himself that he was a persecutor before he became an apostle, [2] still this is not enough for any man who examines before he believes, since even the Lord Himself did not bear witness of Himself. [3] But let them believe without the Scriptures, if their object is to believe contrary to the Scriptures. [4] Still they should show, from the circumstance which they allege of Peter’s being rebuked by Paul, that Paul added yet another form of the gospel besides that which Peter and the rest had previously set forth. ”

“ But the fact is, [5] having been converted from a persecutor to a preacher, he is introduced as one of the brethren to brethren, by brethren—to them, indeed, by men who had put on faith from the apostles’ hands. ”