I never saw the Messenger of Allah ﷺ pray sitting down until he became advanced in age. Then he would pray seated, reciting while sitting, and when about thirty or forty verses of the surah remained, he would stand and recite them, then bow.
أخبرنا إسحق بن إبراهيم قال أنبأنا عيسى بن يونس قال حدثنا هشام بن عروة عن أبيه
ما رأيت رسول الله ﷺ صلى جالسا حتى دخل في السن فكان يصلي وهو جالس يقرأ فإذا غبر من السورة ثلاثون أو أربعون آية قام فقرأ بها ثم ركع
Bukhari narrated it in tahajjud, chapter "If he prayed sitting and then became well," etc, hadith: 1118, etc, hadith: 731, from the hadith of Hisham, and Muslim, prayer of travelers, chapter permitting optional prayer standing or sitting, similarly, and it is in Kubra, hadith: 1356...