The Messenger of Allah ﷺ used to pray thirteen rak'ahs, observing six rak'ahs in pairs including the two rak'ahs of dawn prayer. He would observe witr and five rak'ahs. He sat only in the last of them.  

كَانَ رَسُولُ اللَّهِ ﷺ يُصَلِّي ثَلاَثَ عَشْرَةَ رَكْعَةً بِرَكْعَتَيْهِ قَبْلَ الصُّبْحِ يُصَلِّي سِتًّا مَثْنَى مَثْنَى وَيُوتِرُ بِخَمْسٍ لاَ يَقْعُدُ بَيْنَهُنَّ إِلاَّ فِي آخِرِهِنَّ  

[Machine] Aisha, the wife of the Prophet ﷺ , said: "The Messenger of Allah ﷺ used to pray thirteen rak'ahs during the night, two by two, after Fajr prayer and before sunrise. He used to pray eleven rak'ahs during the night, six of which were prayed in pairs, and he performed Witr prayer with five rak'ahs, without sitting in between them."  

عَنْ عَائِشَةَ زَوْجِ النَّبِيِّ ﷺ قَالَتْ كَانَ رَسُولُ اللهِ ﷺ يُصَلِّي مِنَ اللَّيْلِ ثَلَاثَ عَشْرَةَ رَكْعَةً بِرَكْعَتَيْهِ بَعْدَ الْفَجْرِ قَبْلَ الصُّبْحِ إِحْدَى عَشْرَةَ رَكْعَةً مِنَ اللَّيْلِ سِتٌّ مِنْهُنَّ مَثْنَى مَثْنَى وَيُوتِرُ بِخَمْسٍ لَا يَقْعُدُ فِيهِنَّ