Hearing of Haymo's promotion, Rabanus Maurus, his old friend, gave him at great length—in a work entitled "De Universo" and divided into 22 books—advice that would help him in the discharge of the episcopal office.
In compliance with Rabanus's suggestions, Haymo stood aloof from the Court of King Louis the German, did not entangle himself in the affairs of the State, preached often and lived solely for the welfare of his diocese.
As might be naturally expected from the exegetical methods of his day, Haymo is not an original commentator; he simply repeats or abridges the Scriptural explanations which he finds in patristic writings.
As a pious monk, and a faithful observer of Rabanus's recommendations, he writes almost exclusively about the moral and mystical senses of the sacred text.
He is also the author of an Epitome of Eusebius's Ecclesiastical History, of a large number of sermons, and of a spiritual work, De amore coelestis patriae.