4 But now as to those who talk vauntingly of Divine Grace, and boast that they understand and can explain Scripture without the aid of such directions as those I now propose to lay down, and who think, therefore, that what I have undertaken to write is entirely superfluous. I would such persons could calm themselves so far as to remember that, however justly they may rejoice in God's great gift, yet it was from human teachers they themselves learned to read. Now, they would hardly think it right that they should for that reason be held in contempt by the Egyptian monk Antony, a just and holy man, who, not being able to read himself, is said to have committed the Scriptures to memory through hearing them read by others, and by dint of wise meditation to have arrived at a thorough understanding of them; or by that barbarian slave Christianus, of whom I have lately heard from very respectable and trustworthy witnesses, who, without any teaching from man, attained a full knowledge of the art of reading simply through prayer that it might be revealed to him; after three days' supplication obtaining his request that he might read through a book presented to him on the spot by the astonished bystanders.
Source: Christian Doctrine (New Advent)