It is narrated from Sayyiduna Anas (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) once rode a horse and fell from it, injuring his right side. So he (peace be upon him) performed one of the (obligatory) prayers sitting, and we also prayed sitting with him. When he finished, he said: "The Imam is appointed to be followed, so do not oppose him. Therefore, when he prays standing, you should also pray standing; when he bows (in ruku‘), you should also bow; and when he says «سمع الله لمن حمده» , you should say «ربنا ولك الحمد» ; and if the Imam prays sitting, then all of you should also pray sitting."