Medieval Benedictine anti-islam manuscripts by Peter of Cluny
Peter used the newly translated material in his own writings on Islam, of which the most important are the Summa totius heresis Saracenorum (The Summary of the Entire Heresy of the Saracens) and the Liber contra sectam sive heresim Saracenorum (The Refutation of the Sect or Heresy of the Saracens). In these works Peter portrays Islam as a Christian heresy that approaches paganism (...). His explicit purpose for commissioning the translation was the conversion of Muslims. For Peter, the point is not to "study" a "religion" but to refute a particularly vile form of Christological heresy, a heresy centered on the denial of Christ's divinity.
While his interpretation of Islam was basically negative, it did manage in “setting out a more reasoned approach to Islam (...) through using its own sources rather than those produced by the hyperactive imagination of some earlier Western Christian writers.” Although this alternative approach was not widely accepted or emulated by other Christian scholars of the Middle Ages, it did achieve some influence among a limited number of Church figures (...).
Source text Wikipedia and the paper by John Tolan "Peter the Venerable on the "Diabolical heresy of the Saracens" " on academia.edu. Illustration: The Consecration of Cluny III by Pope Urban II, 12th century (Bibliothèque Nationale de France), source Wikipedia.