Musnad Ahmad 1153:1743

Waki’ narrated to us, he said: Al-A’mash narrated to us, from Ibrahim, from Al-Aswad, from Aisha, who said: When the Messenger of Allah (peace and blessings of Allah be upon him) became ill with the illness from which he died, Bilal came to him to inform him of the prayer. He said: "Command Abu Bakr to lead the people in prayer." We said: "O Messenger of Allah, Abu Bakr is an *asif* man" — Al-A’mash said: "tender-hearted" — "and whenever he stands in your place, he will weep and will not be able to [recite]. If only you would command Umar?" He said: "Command Abu Bakr to lead the people in prayer." We said: "O Messenger of Allah, Abu Bakr is an *asif* man, and whenever he stands in your place, he will weep and will not be able to. If only you would command Umar to lead the people in prayer?" He said: "Command Abu Bakr to lead the people in prayer, for you are the companions of Yusuf." So we sent for Abu Bakr, and he led the people in prayer. Then the Prophet (peace and blessings of Allah be upon him) felt a lightness in himself, so he went out being supported between two men, his feet dragging on the ground. When Abu Bakr sensed him, he went to step back, but the Prophet (peace and blessings of Allah be upon him) gestured to him: "Stay in your place." The Prophet (peace and blessings of Allah be upon him) came until he sat beside Abu Bakr. Abu Bakr was following the Prophet (peace and blessings of Allah be upon him) in prayer, and the people were following Abu Bakr.