The Book of Qiyam Al-Lail (The Night Prayer) and Voluntary Prayers During the Day
20/53. Chapter:
The length of prostration after witr
Sunan an-Nasai
أَخْبَرَنَا يُوسُفُ بْنُ سَعِيدٍ، قَالَ حَدَّثَنَا حَجَّاجٌ، قَالَ حَدَّثَنَا لَيْثٌ، قَالَ حَدَّثَنِي عُقَيْلٌ، عَنِ ابْنِ شِهَابٍ، عَنْ عُرْوَةَ، عَنْ عَائِشَةَ، قَالَتْ كَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم يُصَلِّي إِحْدَى عَشْرَةَ رَكْعَةً فِيمَا بَيْنَ أَنْ يَفْرُغَ مِنْ صَلاَةِ الْعِشَاءِ إِلَى الْفَجْرِ بِاللَّيْلِ سِوَى رَكْعَتَىِ الْفَجْرِ وَيَسْجُدُ قَدْرَ مَا يَقْرَأُ أَحَدُكُمْ خَمْسِينَ آيَةً .
It was narrated that Aishah said: "The Messenger of Allah (ﷺ) used to pray eleven rak'ahs at night between finishing Isha' prayer and Fajr, apart from the two rak'ahs of Fajr, and he would prostrate for as long as it takes one of you to recite fifty verses.
Reference : Sunan an-Nasa'i 1749In-book reference : Book 20, Hadith 152English translation : Vol. 2, Book 20, Hadith 1750