Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates that once the Messenger of Allah (peace and blessings be upon him) was riding a horse and fell, and his right side was grazed. We went to visit him (peace and blessings be upon him) in his illness. When the time of prayer came, he (peace and blessings be upon him) led the prayer sitting, and we too prayed sitting behind him (peace and blessings be upon him). When he (peace and blessings be upon him) had finished the prayer, he said: "The imam is appointed only to be followed. So when he says the takbir, say the takbir; when he bows, bow; when he raises his head from bowing, raise your heads; when he says 'Sami' Allahu liman hamidah' (Allah hears the one who praises Him), say 'Rabbana wa lakal-hamd' (Our Lord, and to You belongs all praise); when he prostrates, prostrate; and when he prays sitting, all of you pray sitting."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3655
Sayyidah Aishah (may Allah be pleased with her) said: The Messenger of Allah (peace and blessings be upon him) fell ill, and his Companions came to visit him. The Messenger of Allah (peace and blessings be upon him) led the prayer sitting, and the Companions prayed behind him standing, so the Messenger of Allah (peace and blessings be upon him) signalled to them to sit, and they sat down. When he (peace and blessings be upon him) had finished the prayer, he said: "The imam is there only to be followed. So when he bows, bow as well; when he raises his head from bowing, raise your heads as well; and when he prays sitting, pray sitting as well."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3656
Sayyidah Aishah (may Allah be pleased with her) said: When the Messenger of Allah (peace and blessings be upon him) became seriously ill, Sayyiduna Bilal (may Allah be pleased with him) came and informed him (peace and blessings be upon him) of the prayer. He (peace and blessings be upon him) said: "Tell Abu Bakr (may Allah be pleased with him) to lead the people in prayer." Sayyidah Aishah (may Allah be pleased with her) said: I said: O Messenger of Allah! Abu Bakr (may Allah be pleased with him) is a soft-hearted man; how can he stand in your place? Nor will he be able to make the people hear (the Qur'an). If only you would order Umar (may Allah be pleased with him). He (peace and blessings be upon him) said: "Tell Abu Bakr (may Allah be pleased with him) to lead the people in prayer." Sayyidah Aishah (may Allah be pleased with her) said: I said to Sayyidah Hafsah (may Allah be pleased with her): Say to the Messenger of Allah (peace and blessings be upon him) that Abu Bakr (may Allah be pleased with him) is soft-hearted; how can he stand in your (peace and blessings be upon him) place? Nor will he be able to make the people hear (the recitation); if only you would tell Umar (may Allah be pleased with him). So she said it to the Messenger of Allah (peace and blessings be upon him), and the Messenger of Allah (peace and blessings be upon him) said: "You are just like the women of (the story of) Yusuf; go and tell Abu Bakr (may Allah be pleased with him)." So he led the people in prayer. Sayyidah Aishah (may Allah be pleased with her) said: When he (may Allah be pleased with him) had begun the prayer, the Messenger of Allah (peace and blessings be upon him) felt some improvement in himself, and he (peace and blessings be upon him) set out, supported between two men, his legs trailing along the ground. When he (peace and blessings be upon him) entered the mosque, Sayyiduna Abu Bakr (may Allah be pleased with him) sensed his (peace and blessings be upon him) arrival and began to step back, but the Messenger of Allah (peace and blessings be upon him) signalled to him to stay in his place. Then the Messenger of Allah (peace and blessings be upon him) came and sat down on the left side of Sayyiduna Abu Bakr (may Allah be pleased with him). The Messenger of Allah (peace and blessings be upon him) was leading the people in prayer sitting, while Sayyiduna Abu Bakr (may Allah be pleased with him) was standing, following the prayer of the Prophet (peace and blessings be upon him), and the people were following the prayer of Sayyiduna Abu Bakr (may Allah be pleased with him).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3657
(a) Sayyidah Aishah (may Allah be pleased with her) said that the Messenger of Allah (peace and blessings be upon him) was ill, so he ordered Sayyiduna Abu Bakr (may Allah be pleased with him) to lead the prayer. Then the Messenger of Allah (peace and blessings be upon him) felt some improvement in himself, so he came and sat at the side of Sayyiduna Abu Bakr (may Allah be pleased with him). The Messenger of Allah (peace and blessings be upon him) was leading Sayyiduna Abu Bakr (may Allah be pleased with him) in prayer while sitting, and Sayyiduna Abu Bakr (may Allah be pleased with him) was leading the people in prayer while standing.
(b) He (peace and blessings be upon him) offered the prayer sitting during the days of his illness. In this hadith there is evidence for what we pointed to in this chapter. In Sayyiduna Abu Bakr (may Allah be pleased with him) standing while he (peace and blessings be upon him) led the prayer sitting, there is evidence that the earlier command was abrogated, and that the correct position is that the follower prays standing even if the imam prays sitting because of a valid excuse. And success is from Allah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3658
Sayyiduna Imran bin Husayn (may Allah be pleased with him) said: I suffered from piles, so I asked the Messenger of Allah (peace and blessings be upon him) (about how to pray), and he (peace and blessings be upon him) said: "Pray standing; if you are unable, then sitting; and if you are unable to do that either, then lying on your side."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3659