Musnad Abu Ya'la al-Mawsili 108:129

On the authority of Jabir, he said: The Messenger of Allah (peace and blessings of Allah be upon him) rode a horse in Medina, and it threw him onto the stump of a palm tree, so his foot was dislocated. We came to visit him and found him in an upper room of Aisha, praying while sitting. We stood behind him, and he remained silent toward us. Then we came to him another time and found him praying the obligatory prayer. We stood behind him, and he gestured to us, so we sat down. When he finished the prayer, he said: "When the Imam prays sitting, then pray sitting, and when he prays standing, then pray standing. And do not do as the people of Persia do with their dignitaries."