The Messenger of Allah ﷺ prayed in his house while he was ill, so he prayed sitting down, and a group of people prayed standing behind him. He gestured to them to sit down. When he finished, he said, "The imam is appointed only to be followed. When he bows, bow, and when he rises, rise."
حدثنا قتيبة بن سعيد عن مالك عن هشام بن عروة عن أبيه
صلى رسول الله ﷺ في بيته وهو شاك فصلى جالسا وصلى وراءه قوم قياما فأشار إليهم أن اجلسوا فلما انصرف قال إنما جعل الإمام ليؤتم به فإذا ركع فاركعوا وإذا رفع فارفعوا