Sahih Bukhari Volume 006, Book 060, Hadith Number 095.
Narrated By Abdullah bin Abbas : That once he stayed overnight (in the house) of his aunt Maimuna. the wife of the Prophet. He added: I lay on the cushion transversely and Allah's Apostle lay along with his wife in the lengthwise direction of the pillow. Allah's Apostle slept till the middle of the night, either a bit before or a bit after it, and then woke up rubbing the traces of sleep off his face with his hands and then he recited the last ten Verses of Surat-al-Imran, got up and went to a hanging water skin. He then performed the ablution from it, and it was perfect ablution, and then stood up to offer the prayer. I too did the same as he had done, and then went to stand beside him. Allah's Apostle put his right hand on my head and held and twisted my right ear. He then offered two Rakat, then two Rakat, then two Rakat, then two Rakat, then two Rakat. then two Rakat, and finally one Rak'a, the Witr. Then he lay down again till the Muadhdhin (i.e. the call-maker) came to him, whereupon he got up and offered a light two-Rakat prayer, and went out (to the Mosque) and offered the (compulsory congregational) Fajr prayer.