Original sentence: Muslims believe, on the basis of the Qur'an, that humans have corrupted the Injil and Tawrat, and that they are no longer available as the word of God as it was revealed, and that only the Qur'an, which God promised that he will protect, is still true to His original revelation
Edited sentence: As revealed in the Qur'an, Muslims believe that humans have corrupted the  Injil and Tawrat, and that they are no longer available as the word of God as it was revealed, and that only the Qur'an, which God promised that he will protect, is still true to His original revelation