But this one fact raises their [the writers of the New Testament] doctrine more than enough above the world: Matthew, previously tied to the gain of his table, Peter and John going about in their boats—all of them rude, uneducated men—had learned nothing in the school of men that they could pass on to others. Paul, not only a sworn but fierce and murderous enemy, was converted into a new man; this sudden and unhoped-for change shows that he was compelled by heavenly authority to affirm a doctrine that he had assailed. Let these dogs deny that the Holy Spirit came down upon the apostles; or even let them discredit history. Yet the truth cries out openly that these men who, previously contemptible among common folk, suddenly began to discourse so gloriously of the heavenly mysteries must have been instructed by the Spirit.
Institutes of the Christian Religion, Volumes 1 & 2, ed. John T. McNeill, trans. Ford Lewis Battles, The Library of Christian Classics (Louisville, KY: Westminster John Knox Press, 2011) Vol. 1.8.11. p. 91.