Sunan an-Nasa'i, Volume 2, Book 20, Hadith 1719 (DarusSalam) ⓘ
Shu'bah narrated from Qatadah, from Zurarahbin Awfa, from Sa'd bin Hisham, that: Aishah said: "When the Messenger of Allah grew old and put on weight, he prayed seven rak'ahs and only sat in the last of them, and he prayed two rak'ahs while sitting after saying the taslim, and that was nine, O my son! And when the Messenger of Allah offered any prayer he liked to persist in doing so."
أَخْبَرَنَا إِسْمَاعِيلُ بْنُ مَسْعُودٍ، قَالَ حَدَّثَنَا خَالِدٌ، قَالَ حَدَّثَنَا شُعْبَةُ، عَنْ قَتَادَةَ، عَنْ زُرَارَةَ بْنِ أَوْفَى، عَنْ سَعْدِ بْنِ هِشَامٍ، عَنْ عَائِشَةَ، قَالَتْ لَمَّا أَسَنَّ رَسُولُ اللَّهِ صلى الله عليه وسلم وَأَخَذَ اللَّحْمَ صَلَّى سَبْعَ رَكَعَاتٍ لاَ يَقْعُدُ إِلاَّ فِي آخِرِهِنَّ وَصَلَّى رَكْعَتَيْنِ وَهُوَ قَاعِدٌ بَعْدَ مَا يُسَلِّمُ فَتِلْكَ تِسْعٌ يَا بُنَىَّ وَكَانَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِذَا صَلَّى صَلاَةً أَحَبَّ أَنْ يُدَاوِمَ عَلَيْهَا . مُخْتَصَرٌ . خَالَفَهُ هِشَامٌ الدَّسْتَوَائِيُّ .
also referenced under: Hadith 1718 (Reference) & Book 20, Hadith 121 (In-Book)