Al-Shafi'i said: The one who used this as evidence knew that there is no proof in it, and that it is not established, because it is mursal, and because it comes from a man from whom people are averse to narrating.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5076
Ubaydullah bin Abdullah bin Utbah says: I went to 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! Then she narrated a long hadith. She says that the Messenger of Allah (peace and blessings be upon him) sent word to Abu Bakr (may Allah be pleased with him) to lead the people in prayer. The messenger came and said: "The Messenger of Allah (peace and blessings be upon him) is ordering you to lead the people in prayer." Abu Bakr (may Allah be pleased with him), who was a soft-hearted man, said: "O Umar, lead the people in prayer." He said: "You are more entitled to it." So Abu Bakr (may Allah be pleased with him) led the people in those days. Then the Prophet (peace and blessings be upon him) felt some relief, and he (peace and blessings be upon him) came out for the Zuhr prayer supported by two men, one of whom was Abbas (may Allah be pleased with him), while Abu Bakr (may Allah be pleased with him) was leading the prayer. When Abu Bakr (may Allah be pleased with him) saw him (peace and blessings be upon him), he moved back, and the Prophet (peace and blessings be upon him) gestured to him: "Do not move back." The Prophet (peace and blessings be upon him) said to the two of them: "Seat me beside him." So the two of them seated him (peace and blessings be upon him) beside Abu Bakr (may Allah be pleased with him). She says: The people were praying following Abu Bakr (may Allah be pleased with him), and Abu Bakr (may Allah be pleased with him) was praying following the Messenger of Allah (peace and blessings be upon him), while the Messenger of Allah (peace and blessings be upon him) was sitting.
Ubaydullah bin Abdullah says: I went to Abdullah bin Abbas (may Allah be pleased with them both) and said: Shall I present to you what Aishah (may Allah be pleased with her) told me about the illness of the Prophet (peace and blessings be upon him)? He said: "Present it." I presented it to him, and he objected to nothing in it, except that he asked: "Did she name the other man who was with Abbas (may Allah be pleased with him)?" I said: No. He said: "He was Ali (may Allah be pleased with him)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 5077