Sayyiduna Abdullah bin Malik (may Allah be pleased with him) narrates that the Messenger of Allah (peace and blessings be upon him) forgetfully stood up after two rak'ahs without the sitting, and continued his prayer. When he was near the end of his prayer, he performed two prostrations before giving the salam, then gave the salam.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3848