It is narrated from Ubaydullah bin Abdullah that he said: I went to Sayyidah Aishah (may Allah be pleased with her) and said: Will you tell me about the illness of the Prophet (peace and blessings be upon him)? She said: Certainly. When the Prophet (peace and blessings be upon him) became ill, he (peace and blessings be upon him) asked: "Have the people prayed?" I said: No, O Messenger of Allah! They are waiting for you. He (peace and blessings be upon him) said: "Put water in the tub for me." Sayyidah Aishah (may Allah be pleased with her) said: The water was put out, and he (peace and blessings be upon him) bathed, then tried to get up, but he (peace and blessings be upon him) fainted. Then he came round and asked: "Have the people prayed?" He was told: They are waiting for you. Then he (peace and blessings be upon him) told them to put water in the tub, and he bathed, then tried to get up, but again he fainted. Then he came round and asked: "Have the people prayed?" He was told: They are waiting for you. Then he (peace and blessings be upon him) told them to put water in the tub, and he bathed, then tried to get up, but again he fainted. Then he regained consciousness and asked: "Have the people prayed?" It was said: The people are waiting for you, and they are sitting in the mosque for the Isha prayer. So he (peace and blessings be upon him) sent word to Sayyiduna Abu Bakr (may Allah be pleased with him) to lead the prayer. When Sayyiduna Abu Bakr (may Allah be pleased with him) received the message, he told Sayyiduna Umar (may Allah be pleased with him) to lead the prayer, because Sayyiduna Abu Bakr (may Allah be pleased with him) was very tender-hearted. Sayyiduna Umar (may Allah be pleased with him) replied that he was more entitled to it, so after that Sayyiduna Abu Bakr (may Allah be pleased with him) kept leading the prayers. One day he (peace and blessings be upon him) felt some improvement, and, supported by two men, one of whom was Sayyiduna Abbas (may Allah be pleased with him), he came to the mosque at the time of Zuhr while Sayyiduna Abu Bakr (may Allah be pleased with him) was leading the prayer. When Sayyiduna Abu Bakr (may Allah be pleased with him) saw that he (peace and blessings be upon him) had come, he began to step back. He (peace and blessings be upon him) gestured to him not to step back and said: "Seat me beside him." So he (peace and blessings be upon him) was seated beside Sayyiduna Abu Bakr (may Allah be pleased with him). Sayyiduna Abu Bakr (may Allah be pleased with him) was following him (peace and blessings be upon him) and the people were following Sayyiduna Abu Bakr (may Allah be pleased with him), while the Prophet (peace and blessings be upon him) was sitting. Ubaydullah said: I went to Sayyiduna Abdullah bin Abbas (may Allah be pleased with them both) and he said: Tell me what Sayyidah Aishah (may Allah be pleased with her) related to you about the illness of the Prophet (peace and blessings be upon him). So I told him, and he confirmed all of it and said: Did she not tell you the name of the other man who was with Sayyiduna Abbas (may Allah be pleased with him)? I said: No. He said: He was Sayyiduna Ali (may Allah be pleased with him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قتال أهل البغي / 16581