In one of my early Introduction to Islam classes, we were asked to write a short research paper on a related subject of our own choosing. We had already learned that Muslims believed Christians and Jews had corrupted or deliberately changed the texts of the Old and New Testaments, so I thought I would look at the historical evidence for that belief.
At the time, Temple University had a well-known religion department with an equally well-stocked library. Looking at the rows and rows of books in the religion section, I was eager to begin my research. To my surprise, I could find no evidence to support the proposition. There were no names, dates, or examples of the corruption that had supposedly taken place.
Even before this, I thought the Muslim claim was rather strange. Early Christians, including almost all of the original followers of Jesus, were killed for their beliefs and this persecution continued for hundreds of years. People don't deliberately change their sacred texts and then willingly die in defense of the falsehoods. Many people have given their lives for false causes, but they believed they were true. You don't die for something you know is wrong.
Later I realized that the Muslim allegation was based upon one simple fact. The Quran is different from the Bible. Since Muslims believe the Quran is perfect, the a priori assumption is that the earlier text was corrupted. The Quran says Jesus was not crucified. The Bible says he was, so the Christians must have changed their text. Muhammad said the Torah predicted that a messenger from Allah named Ahmad (a form of Muhammad) would come. Since the Torah does not say that, the Jews must have removed the reference. Muhammad taught that Allah prevented prophets from committing major sins. The spicy story of David and Bathsheba must have been inserted by those nasty Jews; King David would not really have done that.
Muslims still believe that our Christian and Jewish ancestors deliberately changed their sacred texts. The headlines in the Saudi press for the past few days have been devoted to King Abdallah's recent call for an "Interfaith Dialogue". Six hundred Muslim scholars met in Mecca this weekend to prepare the Muslim positions for this dialogue. A Saudi scholar was interviewed on TV recently about the upcoming dialogue. When he was asked if Islam had come to do away with Judaism and Christianity the scholar replied, "Islam did not get rid of their religions. They contaminated, changed, altered, and distorted their holy books. We accept that their religions exist, but we tell them that they have changed them, and that they know the books they have are not the divine gospel and the divine Torah. We want to bring them back to their original religion."