Gregory was one of the spiritual teachers of the Middle Ages. Most of his writings belong to the first period of the episcopate. The famous work Regula Pastoralis, whose formative content for the clergy was made into a formation manual throughout the Middle Ages is from 591. He wrote his Dialogi between 593-594. Particularly, the collection of 954 Gregorian letters, known as the Registrum epistularum, is of great importance for the study of the 590-604 historical period, in all its aspects