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. (Using translation from Abū Dāʾūd 1359)
كَانَ رَسُولُ اللهِ ﷺ يُصَلِّي ثَلَاثَ عَشْرَةَ رَكْعَةً بِرَكْعَتَيْهِ قَبْلَ الصُّبْحِ يُصَلِّي سِتًّا مَثْنَى مَثْنَى وَيُوتِرُ بِخَمْسٍ لَا يَقْعُدُ بَيْنَهُنَّ إِلَّا فِي آخِرِهِنَّ