The question how the Qur'an was collected into a book form is among those topics which has led some to believe in interpolation or tampering having occurred in the Qur'an. The process, as generally described, makes such changes appear inevitable.
It was therefore necessary to attend to this discussion with a view to establishing that no interpolation, alterations or omissions have occurred in the Qur'an.
Actually, the pristine quality of the Qur'an became doubtful because it was believed that Abu Bakr ordered its compilation after 70 reciters of the Qur'an were killed in the battle of Bir Maunah, and four hundred in the battle of Yamamah. Fearing that the Qur'an would be lost and forgotten by the believers, Umar and Zaid b. Thabit undertook the task of collection from scripts found on palm branches, pieces of cloth and covers, and also from the memory of the Muslims, provided that two witnesses gave testimony that it was from the Qur'an. There are several reports which indicate that such an exercise was indeed carried out. When a compiler is not infallible, one can safely expect an element of error to creep in. Those who compile the widely scattered poems of one single poet could give you various versions of the couplets. These variations are usual, leading finally to the belief that some tampering has occurred. It is quite possible that someone, in spite of having actually heard the Prophet (peace be upon him and his progeny) recite verses from the Qur'an, did not venture to present them because he could not provide two witnesses. Thus, an omission becomes quite probable.
The answer to this is that the doubt becomes valid only if the reports about compilation of Qur'an are deemed credible. So, it is imperative that we mention those reports and analyse them critically.