He had particular contempt for the ulema, writing that: They recite their sacred books, although the fact informs me that these are fiction from first to last. Then perish the fools who forged the religious traditions or interpreted them!
In 1280, the Jewish philosopher, Ibn Kammuna, criticized Islam in his book Examination of the Three Faiths.
Islam's sensual descriptions of paradise led many Christians to conclude that Islam was not a spiritual religion, but a material one.
Although sensual pleasure was also present in early Christianity, as seen in the writings of Irenaeus, the doctrines of the former Manichaean Augustine of Hippo led to broad repudiation of bodily pleasure in both life and the afterlife.
The evil angel modifies and corrupts the original message given to Ozim by Osius, and renames Ozim Muhammad.
From this followed the erroneous teachings of Islam, according to the Tultusceptrum.
According to the monk Bede Muhammad was foretold in Genesis , which describes Ishmael as "a wild man" whose "hand will be against every man".
Bede says about Muhammad: "Now how great is his hand against all and all hands against him; as they impose his authority upon the whole length of Africa and hold both the greater part of Asia and some of Europe, hating and opposing all."Show me just what Muhammad brought that was new and there you will find things only evil and inhuman, such as his command to spread by the sword the faith he preached.
John claimed an Arian monk (whom he did not know was Bahira) influenced Muhammad and viewed the Islamic doctrines as nothing more than a hodgepodge culled from the Bible.
Writing on Islam's claim of Abrahamic ancestry, John explained that the Arabs were called "Saracens" (Greek Σαρακενοί, Sarakenoi) because they were "empty" (κενός, kenos, in Greek) "of Sarah".