Musnad al-Humaydi

Sayyiduna Anas bin Malik (may Allah be pleased with him) narrates: The Noble Prophet (peace and blessings be upon him) fell from a horse and his right side was injured. We came to visit him to inquire about his health. The time for prayer arrived, so the Noble Prophet (peace and blessings be upon him) led us in prayer while sitting. We also performed the prayer sitting behind him. When the Noble Prophet (peace and blessings be upon him) completed the prayer, he said: “Indeed, the Imam is appointed so that he may be followed. When he says the takbir, you also say the takbir. When he goes into ruku‘, you also go into ruku‘. When he rises (from ruku‘), you also rise. When he recites «سَمِعَ اللهُ لِمَنْ حَمِدَهُ», you recite «رَبَّنَا لَكَ وَالْحَمْدُ». When he goes into sajdah, you also go into sajdah. When he performs the prayer sitting, you also perform the prayer sitting.”