St. Augustine writes in On Christian Doctrine:
[A] man who is resting upon faith, hope and love, and who keeps a firm hold upon these, does not need the Scriptures except for the purpose of instructing others. Accordingly, many live without copies of the Scriptures, even in solitude, on the strength of these three graces. So that in their case, I think, the saying is already fulfilled: “Whether there be prophecies, they shall fail; whether there be tongues, they shall cease; whether there be knowledge, it shall vanish away.” Yet by means of these instruments (as they may be called), so great an edifice of faith and love has been built up in them, that, holding to what is perfect, they do not seek for what is only in part perfect—of course, I mean, so far as is possible in this life; for, in comparison with the future life, the life of no just and holy man is perfect here. Therefore the apostle says: “Now abides faith, hope, charity, these three; but the greatest of these is charity:” because, when a man shall have reached the eternal world, while the other two graces will fail, love will remain greater and more assured. [I.xxxix.43; emphasis added]
The Doctor is not saying that Scripture has no use; he is not saying that Scripture is unnecessary for any Christian at all. It is useful for teaching, as he says (and of course as Scripture says). Not every Christian rises to the measure of perfection in this life that St. Augustine observes in some men of his day; indeed, it seems that in his humility he would not even include himself among those who no longer need the Bible.
One thing that he is undeniably saying, however, is that the Bible is not a sine qua non of the godly Christian life. A man can, in St. Augustine’s view here, live a life of holiness and godliness without use of the Scriptures—beyond their usefulness for teaching others. The implication is that we may not ipso facto assume that a Christian without a Bible is somehow substandard (or worse, a Christian in name only).
Whatever else we may say about St. Augustine’s view, we may assuredly say that it is contrary to the typical evangelical Protestant’s.
I have seen some Protestants suggest that perhaps this view was not one held by the saint in his maturity, when his views were more well-developed. I do not consider this to be a credible stance. St. Augustine worked on the book in 427, near the end of his life, and it is pretty unbelievable to me that he would have left this portion un-amended if he found it to be contrary to what he believed at the end of his life.
I have seen at least one Protestant try to turn the passage on its head entirely, pretending (incredibly) that the point is that every Christian needs the Bible for purposes of instructing others. Certainly it is true that in this passage St. Augustine does affirm the Scripture’s usefulness for teaching. But to attempt to spin the thing so as to claim that this usefulness is the very point he had in view is simply ridiculous in the extreme. The point is unambiguous: not every Christian requires the Scripture for godly living. Protestants who think otherwise ought to have the integrity to concede that on this point St. Augustine was most assuredly not one of them.