Sunni literature contains reports that suggest that some of the revelations had already been lost before the collection of the Quran initiated by Abu Bakr. In one report, 'Umar was once looking for the text of a specific verse of the Quran on stoning as a punishment for adultery, which he remembered. Later, he discovered that the only person who had any record of that verse had been killed in the battle of Yamama and as a result the verse was lost. Some of the Companions recalled that same verse, one person being 'A'isha, Muhammad's youngest wife. She is believed to have said that a sheet on which two verses, including the one on stoning, were under her bedding and that after Muhammad died, a domestic animal got into the room and ate the sheet. Experts on hadith literature have rejected this hadith, as all routes of transmission either contain narrators charged with dishonesty in disclosing sources or simply conflict with the majority version of the report, which all have authentic routes of transmission but omit the part about the piece of paper being eaten. Certain Shia scholars state that Ali's predecessors wilfully excluded all references to the right of Ali to be the caliph after Muhammad died. Some Shias questioned the integrity of the Uthmanic codex, stating that two surahs, "al-Nurayn" (The Two Lights) and "al-Walayah" (the Guardianship), which dealt with the virtues of Muhammad's family, were removed. Al-Khoei addresses this issue and argues for the authenticity and completeness of the Quran on the basis that it was compiled during the lifetime of Muhammad. His argument is based on hadiths and on critically analysing the situation during and after the life of Muhammad. He states that the collection of the Quran by Abu Bakr, Umar, and Uthman occurred significantly after the caliphate was decided, and so if Ali's rule had been mentioned, there would have been no need for the Muslims to gather to appoint someone. The fact that none of the Companions mentioned this supposed alteration, either at the beginning of the caliphate or after Ali became caliph, is regarded as proof that this alteration did not occur. Al-Khoei also argues that by the time 'Uthman became caliph, Islam had spread to such an extent that it was impossible for anyone to remove anything from the Quran. Uthman could have altered the text but he would have been