It is narrated from Umm Mubashshir (may Allah be pleased with her): I came to the Messenger of Allah (peace and blessings be upon him) during the illness in which he (peace and blessings be upon him) passed away, and I said: "O Messenger of Allah! May my father and mother be sacrificed for you, what do you perceive regarding this suffering of yours? For I consider the cause of my son's death to be none other than that poisoned food which he ate with you at Khaybar." Her son, Bishr bin al-Bara' bin Ma'rur, had died before the Prophet (peace and blessings be upon him). The Messenger of Allah (peace and blessings be upon him) said: "And I too consider nothing other than that to be the cause (of my suffering). This is the time when my aorta is being severed." This hadith is sahih (authentic) on the condition of the two Shaykhs (Bukhari and Muslim), but they did not record it.