Sayyidah Aishah (may Allah be pleased with her) says: When the illness of the Messenger of Allah (peace and blessings be upon him) grew severe, Bilal (may Allah be pleased with him) came to inform the Prophet (peace and blessings be upon him) of the prayer. He (peace and blessings be upon him) said: "Tell Abu Bakr to lead the people in prayer." I said: O Messenger of Allah, Abu Bakr (may Allah be pleased with him) is tender-hearted; when he stands in your (peace and blessings be upon him) place, he will not be able to make his voice heard to the people. If only you would order Umar (may Allah be pleased with him). He (peace and blessings be upon him) said: "Tell Abu Bakr to lead the people in prayer." I said to Hafsah (may Allah be pleased with her): Say this to the Prophet (peace and blessings be upon him): that Abu Bakr is soft-hearted; when he stands in your (peace and blessings be upon him) place, he will not be able to make his voice heard to the people; if only you would order Umar (may Allah be pleased with him). She said this to the Prophet (peace and blessings be upon him), and the Prophet (peace and blessings be upon him) said: "You are just like the women of Yusuf. Tell Abu Bakr to lead the people in prayer." So they told Abu Bakr (may Allah be pleased with him), and he led the people in prayer. When Abu Bakr (may Allah be pleased with him) began the prayer, the Prophet (peace and blessings be upon him) felt some relief, and he (peace and blessings be upon him) got up supported by two men, his feet (peace and blessings be upon him) drawing lines on the ground as they touched it. When he (peace and blessings be upon him) entered the mosque and Abu Bakr (may Allah be pleased with him) sensed his (peace and blessings be upon him) arrival, he (may Allah be pleased with him) began to move back. He (peace and blessings be upon him) gestured: "Stay in your place." Then the Prophet (peace and blessings be upon him) sat down on the left side of Abu Bakr (may Allah be pleased with him). She says: The Prophet (peace and blessings be upon him) led the people in prayer sitting, and Abu Bakr (may Allah be pleased with him) was standing. Abu Bakr (may Allah be pleased with him) was following the prayer of the Prophet (peace and blessings be upon him), and the people were following the prayer of Abu Bakr (may Allah be pleased with him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5079