Sahih al-Bukhari Book 10, Hadith 83
Once Allah's Messenger (ﷺ) rode a horse and fell down and the right side (of his body) was injured. He
offered one of the prayers while sitting and we also prayed behind him sitting. When he completed the
prayer, he said, "The Imam is to be followed. Pray standing if he prays standing and bow when he
bows; rise when he rises; and if he says, 'Sami`a l-lahu-liman hamidah, say then, 'Rabbana wa laka lhamd'
and pray standing if he prays standing and pray sitting (all of you) if he prays sitting."
Humaid said: The saying of the Prophet (ﷺ) "Pray sitting, if he (Imam) prays sitting" was said in his
former illness (during his early life) but the Prophet (ﷺ) prayed sitting afterwards (in the last illness) and
the people were praying standing behind him and the Prophet (ﷺ) did not order them to sit. We should
follow the latest actions of the Prophet.
the mother of the believers: Allah's Messenger (ﷺ) during his illness prayed at his house while sitting whereas some people prayed behind him standing. The Prophet (ﷺ) beckoned them to sit down. On completion of the prayer, he said, 'The Imam is to be followed: bow when he bows, raise up your heads (stand erect) when he raises his head and when he says, 'Sami`a l-lahu liman hamidah' (Allah heard those who sent praises to Him) say then 'Rabbana wa laka l-hamd' (O our Lord! All the praises are for You), and if he prays sitting then pray sitting."
(and he was not a liar) When Allah's Messenger (ﷺ) said, "Sami`a l-lahu liman hamidah" none of us bent his back (for prostration) till the Prophet (ﷺ) prostrated and then we would prostrate after him.