They did not appraise Allah with true appraisal
When weak souls distorted previous sacred books, they left evidence behind their distortion. If you had read the Qur’an and compared it to the distorted Bible and Torah, you would see the difference.
Allah said : ( interpretation of the meaning ) : { And they did not appraise Allah with true appraisal when they said, " Allah did not reveal to a human being anything." Say, "Who revealed the Scripture that Moses brought as light and guidance to the people? You [Jews] make it into pages, disclosing [some of] it and concealing much. And you were taught that which you knew not - neither you nor your fathers." Say, " Allah [revealed it]." Then leave them in their [empty] discourse, amusing themselves. } Quran ( 6 : 91 )