Musannaf Ibn Abi Shayba 3:4785

Yazid ibn Harun narrated to us, he said: Sufyan ibn Husayn informed us, from al-Zuhri, from Anas, who said: When the Messenger of Allah (may Allah bless him and grant him peace) became ill in the illness in which he died, Bilal came to him and informed him of the prayer. He said: "O Bilal, you have announced it, so whoever wishes, let him pray, and whoever wishes, let him leave it." He said: "O Messenger of Allah, then who shall lead the people in prayer?" He said: "Command Abu Bakr to lead the people in prayer." When Abu Bakr stepped forward, the curtains were raised from the Messenger of Allah (may Allah bless him and grant him peace), and we looked at him as if he were a white sheet, wearing a *khamisa* (garment). Abu Bakr thought that he wanted to come out, so he stepped back. The Messenger of Allah (may Allah bless him and grant him peace) signaled to him to pray where he was. So Abu Bakr prayed, and we did not see the Messenger of Allah (may Allah bless him and grant him peace) again until he died on that day.