Cassiodorus and Augustine were the only patristic authors who left complete commentaries on the Psalms; but whereas in Augustine’s there’a lightning-flash of insight on every other page, Cassiodorus’ insights come much less frequently. Unlike Augustine, who was explaining the Psalms to his people, Cassiodorus was writing for monks, and one gets the impression that he was trying to help them overcome the boredom that can come from over-familiarity.
Although Psalm Ps 51 is a duplicate of Psalm 13, Cassiodorus gives two different interpretations of the one Psalm, and at the conclusion of his commentary, a reflection on sameness and difference uses some lovely images of the variegated beauty of the Scriptures:
We ought to give careful attention to the differences and similarities in these two psalms [Ps 51(52) and Ps 13(14)], where the same words yield different understandings. The clearest evidence of the brilliance of the Scriptures is that in the same words we are to understand different realities of the one faith. If gems radiate different light and colors, if birds are bright with varied colors, if the same body of a chameleon appears green at one moment, blue at another, rosy at another, pale at another, why should the Scriptures not have different understandings; after all, they are often compared to abysses. The sea shimmers differently as it ripples. This is why the orthodox Fathers say different things about a passage, and yet all of them are listened to with benefit. That’s why one of ours [St. Jerome] said: “The Scriptures are a pearl that can be pierced from every side.” (Cassiodorus on Ps 52, conclusion; PL 70, 381)