96 In fact, nothing could have been devised more likely to instruct and benefit the pious reader of sacred Scripture than that, besides describing praiseworthy characters as examples, and blameworthy characters as warnings, it should also narrate cases where good men have gone back and fallen into evil, whether they are restored to the right path or continue irreclaimable; and also where bad men have changed, and have attained to goodness, whether they persevere in it or relapse into evil; in order that the righteous may be not lifted up in the pride of security, nor the wicked hardened in despair of cure.
And even those passages in Scripture which contain no examples or warnings are either required for connection, so as to pass on to essential matters, or, from their very appearance of superfluity, indicate the presence of some secret symbolic meaning. For in the books we speak of, so far from there being a want or a scarcity of prophetical announcements, such announcements are numerous and distinct; and now that the fulfillment has actually taken place, the testimony thus borne to the divine authority of the books is irresistibly strong, so that it is mere madness to suppose that there can be any useless or unmeaning passages in books to which all classes of men and of minds do homage, and which themselves predict what we see thus actually coming to pass.
Source: Reply to Faustus the Manichaean (New Advent)