Musnad Abu Ya'la al-Mawsili 1:90

'Abd al-'Aziz ibn Abi Salamah al-'Umari narrated to us, Ibrahim ibn Sa'd narrated to us, from al-Zuhri, from Anas ibn Malik: Hudhayfah ibn al-Yaman came to 'Uthman ibn 'Affan while he was campaigning with the people of al-Sham in the conquest of Armenia and Azerbaijan alongside the people of Iraq. Hudhayfah was alarmed by their differences in recitation. Hudhayfah said to 'Uthman, "O Commander of the Faithful, save this nation before they differ regarding the Book, as the Jews and the Christians differed." So 'Uthman sent to Hafsah, "Send us the manuscripts so that we may copy them into codices (masahif), then we will return them to you." Hafsah sent them to 'Uthman. 'Uthman ordered Zayd ibn Thabit, 'Abd Allah ibn al-Zubayr, Sa'id ibn al-'As, and 'Abd al-Rahman ibn al-Harith ibn Hisham to copy them into the codices. He said to the three Qurayshi men, "If you and Zayd ibn Thabit differ regarding anything of the Qur'an, write it in the tongue of Quraysh, for it was revealed in their tongue." They did so. When the manuscripts had been copied, 'Uthman returned the manuscripts to Hafsah and sent a codex of what they had copied to every region, and he ordered that whatever else contained the Qur'an in any manuscript or codex be erased or burned. Ibrahim said: Al-Zuhri said: Kharijah ibn Zayd ibn Thabit informed me that he heard Zayd ibn Thabit say, "I missed an ayah from Surat al-Ahzab when we were copying the codices, and I used to hear the Messenger of Allah (may Allah bless him and grant him peace) reciting it. So I searched for it and found it with Khuzaymah ibn Thabit al-Ansari: 'Among the believers are men who have been true to what they pledged to Allah' (Surat al-Ahzab, ayah 23). So I attached it to its surah in the codex."