I never saw the Messenger of Allah ﷺ perform any of the night prayer except standing, until he grew old. Then he began to pray sitting, and when about forty or thirty verses of his recitation remained, he would stand, recite them, and then prostrate.
حدثنا أبو مروان العثماني حدثنا عبد العزيز بن أبي حازم عن هشام بن عروة عن أبيه
ما رأيت رسول الله ﷺ يصلي في شيء من صلاة الليل إلا قائما حتى دخل في السن فجعل يصلي جالسا حتى إذا بقي عليه من قراءته أربعون آية أو ثلاثون آية قام فقرأها وسجد
Bukhari narrated it in "Shortening the Prayer," chapter, "If someone prays sitting, then feels better or finds strength, he completes the rest of the prayer," hadith 1118, and Muslim, "Prayer of Travelers," the aforementioned chapter, hadith 731, from the hadith of Hisham, with a similar meaning. Busiri said, this isnad is sahih, and its narrators are trustworthy.