Messenger of God." Some authors believe that, as long as Muhammad was alive, there was always the expectation of further revelation as well as occasional abrogations. Any formal collection of the material already revealed could not properly be considered a complete text. Abu Bakr According to Sunni scholars, during the life of Muhammad parts of the Quran, though written, were scattered among his companions, much of it as private possession. The number of scribes was 43 companions. And there were many people who though were not scribes also were complete memorizers. After Muhammad's death, Abu Bakr initially exercised a policy of laissez faire as well. This policy was reversed after the Battle of Yamama in 633. During the battle, 70 Muslims who had memorized the Quran were killed. The death of Salim, however, was most significant, as he was one of the very few who had been entrusted by Muhammad to teach the Quran. Consequently, upon Umar's insistence, Abu Bakr ordered the collection of the hitherto scattered pieces of the Quran into one copy. Zayd ibn Thabit, Muhammad's primary scribe, was assigned the duty of gathering all of the Quranic text. He gives an insight into what happened during the meeting between Abu Bakr, Umar, and himself: " Abu Bakr sent for me at a time when the Yamama battles had witnessed the martyrdom of numerous Companions. I found 'Umar bin al-Khattab with him. Abu Bakr began, Umar has just come to me and said, 'In the Yamama battles death has dealt most severely with the qurra',[Reciters of the Quran] and I fear it will deal with them with equal severity in other theatres of war. As a result much of the Quran will be gone. " 'I am therefore of the opinion that you should command the Quran be collected.'" Abu Bakr continued, "I said to 'Umar, 'How can we embark on what the Prophet never did?' 'Umar replied that it was a good deed regardless, and he did not cease replying to my scruples until Allah reconciled me to the undertaking, and I became of the same mind as him. Zaid, you are young and intelligent, you used to record the revelations for Muhammad, and we know nothing to your discredit. So pursue the Quran and collect it together." By Allah, had they asked me to move a mountain it could not have been weightier than what they