A man said, "O Messenger of Allah ﷺ! How is the prayer of the night?" He said, "Two rakʿat followed by two rakʿat and so on, and when you apprehend the approaching dawn, offer one rakʿa as witr."  

يَا رَسُولَ اللَّهِ كَيْفَ صَلاَةُ اللَّيْلِ قَالَ مَثْنَى مَثْنَى فَإِذَا خِفْتَ الصُّبْحَ فَأَوْتِرْ بِوَاحِدَةٍ  

The prayer of the Prophet ﷺ used to be of thirteen rakʿat, i.e. of the night prayer.  

كَانَ صَلاَةُ النَّبِيِّ ﷺ ثَلاَثَ عَشْرَةَ رَكْعَةً يَعْنِي بِاللَّيْلِ  

I asked Aisha about the night prayer of Messenger of Allah ﷺ and she said, "It was seven, nine or eleven rakʿat besides the two rakʿat of the Fajr prayer (i.e. Sunna). "  

عَنْ صَلاَةِ رَسُولِ اللَّهِ ﷺ بِاللَّيْلِ فَقَالَتْ سَبْعٌ وَتِسْعٌ وَإِحْدَى عَشْرَةَ سِوَى رَكْعَتَىِ الْفَجْرِ  

The Prophet ﷺ used to offer thirteen rakʿat of the night prayer and that included the witr and two rakʿat (Sunna) of the Fajr prayer.  

كَانَ النَّبِيُّ ﷺ يُصَلِّي مِنَ اللَّيْلِ ثَلاَثَ عَشْرَةَ رَكْعَةً مِنْهَا الْوِتْرُ وَرَكْعَتَا الْفَجْرِ