In the case of scriptures that Allah (the Exalted) revealed to the people, human beings have attempted to preserve them. In spite of this, we now have numerous different versions of the same book, which indicates a failure of the preservation attempt.
No one can deny that Allah revealed the Torah and the Gospel to Prophets Moses (peace be upon him) and Jesus (pbuh) respectively. But today, can any of their followers put their fingers on a specific version of the Old Testament or the New Testament and say definitively that this is the word of God as revealed to Prophet Jesus or Moses? I leave the answer to the respected reader.