"The night prayer of Messenger of Allah was thirteen Rak'ah, five of which were his Witr, not sitting in any of them except at the end of them. When the Mu'adh-dhin called the Adhan he would stand to perform two light (Rak'ah)."  

كَانَتْ صَلاَةُ النَّبِيِّ ﷺ مِنَ اللَّيْلِ ثَلاَثَ عَشْرَةَ رَكْعَةً يُوتِرُ مِنْ ذَلِكَ بِخَمْسٍ لاَ يَجْلِسُ فِي شَيْءٍ مِنْهُنَّ إِلاَّ فِي آخِرِهِنَّ فَإِذَا أَذَّنَ الْمُؤَذِّنُ قَامَ فَصَلَّى رَكْعَتَيْنِ خَفِيفَتَيْنِ قَالَ وَفِي الْبَابِ عَنْ أَبِي أَيُّوبَ