Sunan an-Nasai Book 7, Hadith 685

أَخْبَرَنَا أَحْمَدُ بْنُ عَمْرِو بْنِ السَّرْحِ، قَالَ أَنْبَأَنَا ابْنُ وَهْبٍ، قَالَ أَخْبَرَنِي ابْنُ أَبِي ذِئْبٍ، وَيُونُسُ، وَعَمْرُو بْنُ الْحَارِثِ، أَنَّ ابْنَ شِهَابٍ، أَخْبَرَهُمْ عَنْ عُرْوَةَ، عَنْ عَائِشَةَ، قَالَتْ كَانَ النَّبِيُّ صلى الله عليه وسلم يُصَلِّي فِيمَا بَيْنَ أَنْ يَفْرُغَ مِنْ صَلاَةِ الْعِشَاءِ إِلَى الْفَجْرِ إِحْدَى عَشْرَةَ رَكْعَةً يُسَلِّمُ بَيْنَ كُلِّ رَكْعَتَيْنِ وَيُوتِرُ بِوَاحِدَةٍ وَيَسْجُدُ سَجْدَةً قَدْرَ مَا يَقْرَأُ أَحَدُكُمْ خَمْسِينَ آيَةً ثُمَّ يَرْفَعُ رَأْسَهُ فَإِذَا سَكَتَ الْمُؤَذِّنُ مِنْ صَلاَةِ الْفَجْرِ وَتَبَيَّنَ لَهُ الْفَجْرُ رَكَعَ رَكْعَتَيْنِ خَفِيفَتَيْنِ ثُمَّ اضْطَجَعَ عَلَى شِقِّهِ الأَيْمَنِ حَتَّى يَأْتِيَهُ الْمُؤَذِّنُ بِالإِقَامَةِ فَيَخْرُجُ مَعَهُ وَبَعْضُهُمْ يَزِيدُ عَلَى بَعْضٍ فِي الْحَدِيثِ ‏.‏

It was narrated that 'Aishah said:"Between the time when he finished 'Isha' prayer and Fajr, the Prophet (S.A.W) used to pray eleven Rak'ahs, saying the Taslim after each two Rak'ahs, then praying Witr as one Rak'ah. He would prostrate for as long as it takes one of you to recite fifty verses, then he would raise his head. When the Mu'adhdhin finished the call to Fajr prayer and he could see the dawn, he would pray two brief Rak'ahs, then he would go out with him." Some of these narrators (Ibn Abi Dhi'b, Yunus and 'Amr bin Al-Harith) added some phrases not mentioned by the others in the Hadith