From his Moralia in Job, Book II, section 1:
Holy Writ is set before the eyes of the mind like a kind of mirror, that we may see our inward face in it; for therein we learn the deformities, therein we learn the beauties that we possess; there we are made sensible what progress we are making, there too how far we are from proficiency. It relates the deeds of the Saints, and stirs the hearts of the weak to follow their example, and while it commemorates their victorious deeds, it strengthens our feebleness against the assaults of our vices; and its words have this effect, that the mind is so much the less dismayed amidst conflicts as it sees the triumphs of so many brave men set before it. Sometimes however it not only informs us of their excellencies, but also makes known their mischances, that both in the victory of brave men we may see what we ought to seize on by imitation, and again in their falls what we ought to stand in fear of. For, observe how Job is described as rendered greater by temptation, but David by temptation brought to the ground, that both the virtue of our predecessors may cherish our hopes, and the downfall of our predecessors may brace us to the cautiousness of humility, so that whilst we are uplifted by the former to joy, by the latter we may be kept down through fears, and that the hearer's mind, being from the one source imbued with the confidence of hope, and from the other with the humility arising from fear, may neither swell with rash pride, in that it is kept down by alarm, nor be so kept down by fear as to despair, in that it finds support for confident hope in a precedent of virtue.