In the 12th century, following the overthrow of the Isma'ili Fatimid dynasty, Saladin (the founder of the Sunni Ayyubid Dynasty) converted Al-Azhar to a Shafi'ite Sunni center of learning.[6][14] Therefore, the Encyclopaedia of Islam (Leiden, 1936, 3rd vol., p. 353) writes that, "He had all the treasures of the palace, including the books, sold over a period of ten years. Many were burned, thrown into the Nile, or thrown into a great heap, which was covered with sand, so that a regular "hill of books" was formed and the soldiers used to sole their shoes with the fine bindings. The number of books said to have disposed of varies from 120,000 to 2,000,000."[15] Abd-el-latif delivered lectures on Islamic medicine at Al-Azhar, while according to legend the Jewish philosopher Maimonides delivered lectures on medicine and astronomy there during the time of Saladin though no historical proof has corroborated this.[16]

https://en.wikipedia.org/wiki/Al-Azhar_University#Conversion_to_Sunniism_under_Saladin

https://en.wikipedia.org/wiki/List_of_book-burning_incidents#Ismaili_Shite_writings_at_Al-Azhar_(by_Saladin)