Abdullah bin Shaqiq (may Allah have mercy on him) said: I asked Aishah (may Allah be pleased with her) about the prayer of the Prophet (peace and blessings be upon him), and she said: He (peace and blessings be upon him) would often pray standing or sitting. When he (peace and blessings be upon him) began the prayer standing, he would also bow standing, and when he began the prayer sitting, he would also bow sitting.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4583
Abdullah bin Shaqiq (may Allah have mercy on him) said: I asked Sayyidah Aishah (may Allah be pleased with her): Did the Prophet (peace and blessings be upon him) pray while sitting? She said: "Yes, when people had worn him (peace and blessings be upon him) down."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4584
Abu Salamah bin Abdur-Rahman said: Aishah (may Allah be pleased with her) told me: The Prophet (peace and blessings be upon him) did not pass away until much of his (peace and blessings be upon him) prayer was performed sitting.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4585
Abdullah bin Urwah narrates from his father that Sayyidah Aishah (may Allah be pleased with her) said: When his (peace and blessings be upon him) body became heavy, he would pray most of his prayers sitting.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4586
Al-Muttalib bin Abi Wada'ah al-Sahmi narrates from Sayyidah Hafsah (may Allah be pleased with her) that she said: I never saw the Prophet (peace and blessings be upon him) pray a voluntary prayer sitting until a year before his death, when he would pray voluntary prayer sitting. And he would recite a surah in slow, measured recitation (tartil), until it became longer than a surah longer than it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4587
Simak narrates from Sayyiduna Jabir bin Samurah (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) did not pass away until he was praying sitting.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4588