(Imām Bukhārī narrates): Qutaibah ibn Sa'īd narrated to us, he said: Laith narrated to us, from Ibn Shihāb, from Anas ibn Mālik, may Allāh be pleased with him, he narrated that:

the Messenger of Allāh ﷺ fell from a horse, so he was injured. Then he led us in prayer sitting, and we too prayed with him sitting. Then after finishing the prayer, he said that the imām is appointed only so that he may be followed; so when he pronounces the takbīr, you pronounce the takbīr; and when he performs rukū', you perform rukū'; and when he raises his head from rukū', you raise your head from rukū'; and when he says "Sami'a Allāhu liman hamidah", you say "Rabbanā laka al-hamd"; and when he performs sajdah, you perform sajdah.