Commentary Purg X 75

Saint Gregory, known as Gregory the Great, was pope from 590 to 604.  His lengthy commentary on the Book of Job (the Moralia), one of the most influential writings of the earlier middle ages, offers a different and happier understanding of Job's story than is prevalent today, insisting that it has a truly 'comic' resolution, rebinding Job to God and restoring his family.  Dante mentions Gregory twice, here and in [Paradiso XX 106-117], in connection with the salvation of Trajan, and he is referred to in the last sphere of the heavens as one of the saved ([Par XXVIII 133]), despite the fact that he had made small errors in listing the orders of the angelic hierarchy (as had Dante himself in Conv.II.v.6) in the Moralia. 

      For information about which popes are saved and which are damned according to the Commedia see C.Inf.VII.46-48.