and dislike for Ali and Fatima are well-documented. Mentioning three different versions of the story, Madelung defers to Caetani, who considers it fabricated. Shia authors similarly dispute the authenticity of these reports, adding that Muhammad had earlier instructed his companions, including Abu Bakr and Umar, to leave Medina on a military campaign against the Byzantines under Usama ibn Zayd. Significance Sunni authors often refer to this event as evidence of Abu Bakr's right to succeed Muhammad, though their accounts of the event might be colored by later Shia-Sunni polemics. Ayoub adds that the prayer argument was likely not a consideration in the early caliphal debate. Lecomte writes that Muhammad respected Abu Bakr but considers the prayer story inconclusive because it does not formally relate to the political leadership of the community. Walker notes that this and similar traditions suggest friendship and trust but are hardly related to succession because Muhammad regularly delegated this task and other positions of authority to others. For the same reason, Shaban goes further and assigns no significance to the prayer story. Hadith of Pen and Paper Shortly before his death, Muhammad asked for writing materials, so that he would "write something, after which you will not be led into error," as reported in the canonical Sunni collection Sahih al-Bukhari. Of those present at Muhammad's bedside, this report continues that his companion Umar protested, "The illness has overwhelmed the prophet. We have the book of God [Quran] and that is enough for us." In some reports by the Sunni Ibn Sa'd (), Umar instead says that Muhammad is raving. A quarrel then broke out at Muhammad's bedside, with some suggesting that his orders should be followed and some siding with Umar to disregard the prophet's request. The argument is said to have saddened Muhammad, who asked them to leave and did not write anything. Some sources write that Muhammad instead gave oral recommendations, which have been recorded differently by various authors. Views The disobedience to Muhammad in this incident has been downplayed by some Sunni scholars, whereas others view this incident as a missed opportunity to formally designate Abu Bakr as the successor. Ibn Kathir () goes further, claiming that Muhammad had publicly appointed Abu Bakr before his final illness. In contrast, the incident is viewed as a calamity and a missed opportunity to designate Ali in Shia sources. In relation to this episode, Madelung quotes