Watt states that the charge of altering the scripture may mean no more than giving false interpretations to some passages, though in contemporary Islam it is taken to refer to textual corruption. The corruption of previously revealed books is referred to as tahrif. The Qur'an also stated that there was nothing surprising in Muhammad's rejection by Jews, as that had occurred to other prophets mentioned in Jewish scripture. Watt claims that the Qur'an "also went on to criticize Jewish exaggerations of their claim to be the chosen people" and argued against the supposed claim of the Jews of Medina "that they alone had a true knowledge of God". The Qur'an also criticized the Jews for believing that Ezra is the Son of God, a claim unattested either in Jewish or other extra-Qur'anic sources. Michael Cook considers the charge of considering Ezra as the Son of God to be petty or obscure. The Encyclopedia Judaica article on Ezra says, "Muhammed claims (Sura 9:30) that in the opinion of the Jews, Uzayr (Ezra) is the son of God. These words are enigma because no such opinion is to be found among the Jews, even though Ezra was singled out for special appreciation (see Sanh. 21b; Yev. 86b)."