Zaid b. Thābit said

Abū Bakr sent for me after the slaughter of those who fought at al-Yamāma and ‘Umar b. al-Khattāb was with him. Abū Bakr told me that ‘Umar had come to him and drawn attention to the extensive slaughter among Qur’ān readers at the battle of al- Yamāma, saying he was afraid that if readers continued to be killed in large numbers at other battles a large amount of the Qur’ān would be lost, and that he therefore thought he should give command that the Qur’ān be collected. He had asked. ‘Umar how he could do a thing which Allah's Messenger ﷺ had not done, and ‘Umar, swearing by Allah that this was best, had kept at him till Allah made him inclined to do that, and he came to hold ‘Umar’s opinion about the matter. Zaid told how Abū Bakr said to him, “You are an intelligent young man whom we do not suspect and you have been writing down the revelation which came to Allah's Messenger ﷺ, so search for the Qur’ān and collect it,” adding: I swear by Allah that if they had imposed on me the transportation of a mountain it would not have been a heavier load for me than the collecting of the Qur’ān which he ordered me to undertake. I asked how they could do a thing which Allah's Messenger ﷺ had not done and Abū Bakr, swearing by Allah that this was best, kept at me till Allah made me in­clined to do what He had made Abū Bakr and ‘Umar inclined to do. I therefore searched for the Qur’ān and collected it from leafless palm branches, white stones and the breasts of men till I found the end of sūra at-Tauba (Qur’ān, 9) with Abū Khuzaima al-Ansārī, not having found it with anyone else: "A messenger from among yourselves has come to you . . .” to the end of Barā'a* (Qur’ān, 9 128-129). The sheets were deposited with Abū Bakr till Allah took him, then with ‘Umar during his lifetime, then with Hafsa, ‘Umar’s daughter. *Tauba and Barā’a are alternative titles of sūra 9. Bukhārī transmitted it.