Musnad Ahmad 1153:1095

Yazid narrated to us, Ibrahim ibn Sa'd informed us, from Salih ibn Kaysan, from al-Zuhri, from 'Urwah, from 'Aishah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) entered upon me on the day in which he became ill, and I said: "Oh, my head!" He said: "I wish that had happened while I was alive, so I could have prepared you and buried you." She said: I said: "Rather, I think that on that day you would be a bridegroom to some of your wives." He said: "And I, oh, my head! Call your father and your brother for me, so that I may write a document for Abu Bakr, for I fear that a speaker might speak or a wisher might wish: 'I am more entitled,' while Allah, the Mighty and Majestic, and the believers refuse [anyone] except Abu Bakr."