It is narrated from Sayyiduna Usayd bin Hudayr (may Allah be pleased with him) that he was one who sighed much (tender-hearted), and he used to lead us in prayer. Once he fell ill and led the prayer sitting. The Messenger of Allah (peace and blessings be upon him) came to visit him, and the people said: O Messenger of Allah! Usayd is our imam; he is ill, and he has led us in prayer sitting. So the Messenger of Allah (peace and blessings be upon him) said: "You too pray behind him sitting, for the imam is appointed only to be followed; so when he prays sitting, you too pray behind him sitting." This hadith has a sahih (authentic) chain of narration, but the two Shaykhs (Bukhari and Muslim) did not record it.