I asked 'A'isha about the prayer of the Messenger of Allah ﷺ. She said: The Messenger of Allah ﷺ would observe prayer (Nafl) in a standing position as well as in a sitting position, and when he commenced the prayer in a standing position, he bowed in this very position, and when he commenced the prayer in a sitting position, he bowed in this very position. (Using translation from Muslim 730e)   

صَلَاةِ رَسُولِ اللهِ ﷺ فَقَالَتْ كَانَ رَسُولُ اللهِ ﷺ يُكْثِرُ الصَّلَاةَ قَائِمًا وَقَاعِدًا فَإِذَا افْتَتَحَ الصَّلَاةَ قَائِمًا رَكَعَ قَائِمًا وَإِذَا افْتَتَحَ الصَّلَاةَ قَاعِدًا رَكَعَ قَاعِدًا  

[Machine] Did the Prophet ﷺ used to pray while sitting? Aisha said, "Yes, after the people crowded around him."  

لِعَائِشَةَ ؓ هَلْ كَانَ النَّبِيُّ ﷺ يُصَلِّي وَهُوَ قَاعِدٌ؟ قَالَتْ نَعَمْ بَعْدَ مَا حَطَمَهُ النَّاسُ  

[Machine] The Messenger of Allah ﷺ did not pass away until he had prayed a lot while sitting.  

رَسُولَ اللهِ ﷺ لَمْ يَمُتْ حَتَّى كَانَ كَثِيرٌ مِنْ صَلَاتِهِ وَهُوَ جَالِسٌ  

[Machine] The most frequent prayer of the Prophet Muhammad ﷺ was when he was sitting and feeling heavy or tired in his body.  

كَانَ أَكْثَرُ صَلَاةِ رَسُولِ اللهِ ﷺ حِينَ ثَقُلَ وَبَدَّنَ وَهُوَ جَالِسٌ  

Never did I see the Messenger of Allah ﷺ observing supererogatory prayer sitting till one year before his death when he would observe Nafl prayer in a sitting position, and he would recite the Surah (of the Qur'an) in such a slow-measured tone (that duration of its recital) became more lengthy than the one longer than this. (Using translation from Muslim 733a)   

مَا رَأَيْتُ رَسُولَ اللهِ ﷺ صَلَّى فِي سُبْحَةٍ قَاعِدًا حَتَّى كَانَ قَبْلَ وَفَاتِهِ بِعَامٍ فَكَانَ يُصَلِّي فِي سُبْحَةٍ قَاعِدًا وَكَانَ يَقْرَأُ بِالسُّورَةِ فَيُرَتِّلُهَا حَتَّى تَكُونَ أَطْوَلَ مِنْ أَطْوَلَ مِنْهَا  

[Machine] That the Prophet did not die until he prayed while sitting.  

أَنَّ النَّبِيَّ ﷺ لَمْ يَمُتْ حَتَّى صَلَّى قَاعِدًا