"I did not see Messenger of Allah (S) praying voluntary prayers sitting until the year before he died. Then he would perform Salat for the voluntary prayers sitting, and he would recite a Surah and prolong it such that it would be longer than the longest of them."
عَنْ حَفْصَةَ زَوْجِ النَّبِيِّ ﷺ أَنَّهَا قَالَتْ مَا رَأَيْتُ رَسُولَ اللَّهِ ﷺ صَلَّى فِي سُبْحَتِهِ قَاعِدًا حَتَّى كَانَ قَبْلَ وَفَاتِهِ ﷺ بِعَامٍ فَإِنَّهُ كَانَ يُصَلِّي فِي سُبْحَتِهِ قَاعِدًا وَيَقْرَأُ بِالسُّورَةِ وَيُرَتِّلُهَا حَتَّى تَكُونَ أَطْوَلَ مِنْ أَطْوَلَ مِنْهَا وَفِي الْبَابِ عَنْ أُمِّ سَلَمَةَ وَأَنَسِ بْنِ مَالِكٍ