It is narrated from Yusuf, the father of Muhammad (may Allah have mercy on him), from Sayyiduna Mu'awiyah bin Abi Sufyan (may Allah be pleased with him), that he led them in prayer and, forgetting, stood up when he was required to sit, and he did not sit. Then, when he reached the last part of the prayer, he performed two prostrations before 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 / 16823