The Messenger of Allah ﷺ led the prayer while he was ill. A group prayed behind him standing, so he gestured to them to sit down. When he finished, he said, "The imam is appointed only to be followed. When he bows, bow. When he rises, rise. And when he prays sitting, pray sitting."
صلى رسول الله ﷺ وهو شاك. فصلى وراءه قوم قياما، فأشار إليهم أن اجلسوا، فلما انصرف قال: إنما جعل الإمام ليؤتم به، فإذا ركع فاركعوا، وإذا رفع فارفعوا، وإذا صلى جالسا فصلوا جلوسا.
Malik narrated it in "Prayer in Congregation" (17), from Hisham bin Urwa, from his father, from Ayesha, who mentioned the same. Bukhari narrated it in "The Adhan" (688), from Abdullah bin Yusuf, from Malik. And Muslim narrated it in "Prayer" (412), through Abdah bin Sulayman, from Hisham, with the same wording.