عَنْ عَائِشَةَ رَضِيَ اللَّهُ عَنْهَا قَالَتْ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ يُوْتِرُ بِتِسْعِ رَكَعَاتٍ وَرَكْعَتَيْنِ وَهُوَ جَالِسٌ فَلَمَّا ضَعُفَ أَوْتَرَ بِسَبْعٍ وَرَكْعَتَيْنِ وَهُوَ جَالِسٌ
Sayyidah Aisha (may Allah be pleased with her) says that the Messenger of Allah (peace and blessings be upon him) used to perform nine rak'ahs of Witr and would offer two rak'ahs sitting. When he became weak, he would perform seven Witr and offer two rak'ahs sitting.