De laudibus sancte crucis

Vincent in the Mirror of History, book 25, chapter 28.

Rabanus the sophist learned man/scholar, second to none of the poets of his time, was the Abbot of Fulda. He discussed many things from the holy scriptures. He also composed a book on the praise of the holy Cross, distinguished by a variety of figures in a difficult and wonderful poem, and sent it to be offered to Pope Sergius.

Antoninus in his Chronicle: second part, title 14, chapter 5, paragraph 1.

He alludes to and supports the same with almost the same words used by Vincent.

Odilo, Abbot of Cluny, in a sermon on the praise of the holy Cross, says this:

Rabanus, abundantly learned in secular science, Catholic in faith, fully taught in spiritual science, wove such a work on the praise of the holy Cross. In weaving it, he perfected it so that nothing more precious to see, more lovely to read, sweeter to retain, or more laborious to write can be found.

Martin in his Chronicle under Louis the Pious, son of Charlemagne:

At that time flourishes Rabanus, a monk and Abbot of Fulda, a great poet, and illustrious in the science of theology.

Platina in his life of Gregory IV:

There are those who write that at the request of Louis, Gregory instituted the celebration of All Saints on the first of November. They say that matter was greatly praised by Rabanus, the monk and distinguished theologian, in poems and prose. For in these two kinds of speaking, as a learned man, he was quite powerful for that time. The same Rabanus also commented on the book of Chronicles and the Maccabees. He also had quite elegant sermons for the people, but the one he had on the celebration of All Saints is praised most of all.

Wernher Rolevinck, the Westphalian Carthusian of Cologne, in the Small Bundle of Times under Louis I.

Rabanus, poet and monk, later Abbot of Fulda, then Archbishop of Mainz, a great doctor, was famous and wrote many things.

Jacobus Philippus of Bergamo in the Supplement to the Chronicles.

Rabanus, monk and Archbishop of Mainz, a most famous theologian and distinguished poet. He was very powerful in prose and verse.

Johannes Trithemius, Abbot of Sponheim, On Ecclesiastical Writers.

Rabanus the German, from the city of Fulda in Buchonia the Beech Forest region: a man most learned in the divine scriptures and nobly taught in secular letters. A most subtle philosopher, rhetorician, astronomer, and poet; to whom Italy produced no similar man, nor did Germany produce an equal. He wrote many volumes both in verse and in prose, especially on the holy scriptures, almost on both testaments, and on the praise of the holy Cross, the beginning of which is "The Lord King of Kings" original: "Rex regum dominus".