It was narrated from Sa'd bin Hisham:That he came to the Mother of the Believers Aishah and asked her about the prayers of the Messenger of Allah (ﷺ). She said: "He used to pray eight rak'ahs at night and pray witr with the ninth, then he would pray two rak'ahs sitting down."
أَخْبَرَنَا مُحَمَّدُ بْنُ عَبْدِ اللَّهِ الْخَلَنْجِيُّ، قَالَ حَدَّثَنَا أَبُو سَعِيدٍ، - يَعْنِي مَوْلَى بَنِي هَاشِمٍ - قَالَ حَدَّثَنَا حُصَيْنُ بْنُ نَافِعٍ، قَالَ حَدَّثَنَا الْحَسَنُ، عَنْ سَعْدِ بْنِ هِشَامٍ، أَنَّهُ وَفَدَ عَلَى أُمِّ الْمُؤْمِنِينَ عَائِشَةَ فَسَأَلَهَا عَنْ صَلاَةِ رَسُولِ اللَّهِ صلى الله عليه وسلم فَقَالَتْ كَانَ يُصَلِّي مِنَ اللَّيْلِ ثَمَانَ رَكَعَاتٍ وَيُوتِرُ بِالتَّاسِعَةِ وَيُصَلِّي رَكْعَتَيْنِ وَهُوَ جَالِسٌ . مُخْتَصَرٌ .
Nesai
The Book of Qiyam Al-Lail (The Night Prayer) and Voluntary Prayers During the Day • Hadith 1724