"The Messenger of Allah ﷺ used to pray eleven rak'ahs, making it odd (witr) by one between the time when he finished 'Isha and dawn, and he would prostrate for as long as it takes one of you to recite fifty verses before raising his head." (Using translation from Nasāʾī 1328)  

عَائِشَةُ كَانَ رَسُولُ اللهِ ﷺ «يُصَلِّي فِيمَا بَيْنَ أَنْ يَفْرُغَ مِنْ صَلَاةِ الْعِشَاءِ إِلَى الْفَجْرِ إِحْدَى عَشْرَةَ رَكْعَةً وَيُوتِرُ بِوَاحِدَةٍ وَيَسْجُدُ سَجْدَةً قَدْرَ مَا يَقْرَأُ أَحَدُكُمْ خَمْسِينَ آيَةً قَبْلَ أَنْ يَرْفَعَ رَأْسَهُ» وَبَعْضُهُمْ يَزِيدُ عَلَى بَعْضٍ فِي الْحَدِيثِ مُخْتَصَرٌ