It wasnarrated from Anas bin Malik that the Prophet (ﷺ) fell fromhishorse and he suffered some lacerations on his right side. We wenttovisit him and the time for prayer came. He led us in prayer sittingdown, and we prayed behind him sitting down. When he finished theprayer he said:
"The Imam is appointed to be followed. When he saysAllahu Akbar, then say Allahu Akbar; when he bows, then bow; when hesays Sami' Allahu liman hamidah, then say Rabbana wa lakal-hamd;whenhe prostrates then prostrate; and if he prays sitting down thenpraysitting down."
English reference: Vol. 1, Book 5, Hadith 1238
Arabic reference: Book 5, Hadith 1296