The Book of Prayer - Travellers
6/16. Chapter:
It is permissible to offer voluntary prayers standing or sitting, and to stand and sit in the same rak`ah
Sahih Muslim
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا عُبَيْدُ اللَّهِ بْنُ مُوسَى، عَنْ حَسَنِ بْنِ صَالِحٍ، عَنْ سِمَاكٍ، قَالَ أَخْبَرَنِي جَابِرُ بْنُ سَمُرَةَ، أَنَّ النَّبِيَّ صلى الله عليه وسلم لَمْ يَمُتْ حَتَّى صَلَّى قَاعِدًا .
Jabir b. Samura reported that the Messenger of Allah (ﷺ) observed (Nafl) prayer sitting before his death.
Reference : Sahih Muslim 734In-book reference : Book 6, Hadith 144USC-MSA web (English) reference : Book 4, Hadith 1599