It is narrated from Sayyiduna al-Mughirah bin Shu'bah (may Allah be pleased with him) that he stood up after the first two rak'ahs (without sitting for the tashahhud). The people alerted him by saying "Subhan Allah", but he did not sit. Then when he had completed his prayer, he performed the two prostrations of forgetfulness after the salam, then said: "The Messenger of Allah (peace and blessings be upon him) did it like this."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 18111