Gregory the Great was pope from 590-604 and left behind a substantial literary heritage. His most ambitious work and one of the most popular works of scriptural exegesis in the middle ages was the Moralia in Iob, commenting the book of Job in 35 books running to over half a million words. Saint Gregory's Commentary on Job was written between 578 and 595, begun when Gregory was at the court of Tiberius II at Constantinople, but finished only after he had already been in Rome for several years.