It is narrated from Yusuf, the father of Muhammad (may Allah have mercy on him), that Mu'awiyah bin Abi Sufyan (may Allah be pleased with him) led them in prayer and, forgetting, stood up when he was required to sit, and he did not sit. Then, when it was the last part of his prayer, he performed two prostrations before giving the salam, and then said: "This is how I saw the Messenger of Allah (peace and blessings be upon him) do it."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 16822