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