Musnad Ahmad Hadith 25346

It is narrated from Aisha (may Allah be pleased with her) that the Prophet (ﷺ) used to perform witr with nine rak‘ahs and then, while sitting, would offer two rak‘ahs. When he became weak, he performed witr with seven rak‘ahs and, while sitting, would offer two rak‘ahs. It is narrated from Zurarah (may Allah be pleased with him) that Sa‘d bin Hisham bin ‘Amir (may Allah be pleased with him) came to the service of Aisha (may Allah be pleased with her)... Then the narrator mentioned the entire hadith and said that the Prophet (ﷺ) used to pray nine rak‘ahs, and in those rak‘ahs he would not sit except after the eighth rak‘ah, and he would remember Allah, praise Him, and supplicate to Him, then he would stand up without saying salam, then stand and pray the ninth rak‘ah, then he would sit, remember Allah, praise Him, and supplicate to Him, then he would say salam, making the salam audible to us, then after saying salam, while sitting, he would pray two rak‘ahs.