I asked 'A'isha whether the Messenger of Allah (ﷺ) observed (Nafl) sitting. She said: Yes, when the people had made him old.
Sahih Muslim Book 6, Hadith 138
← Previous Hadith I asked 'A'isha how the Messenger of Allah (ﷺ) did in the two rak'ahs as he (observed them) sitting. She said: He would recite (the Qur'an) in them, and when he intended to bow, he would stand up and then bowed.

Sahih Muslim Book 6, Hadith 137 Next Hadith → I said to 'A'isha and she made a mention of that (recorded above) about the Messenger of Allah (ﷺ).

Sahih Muslim Book 6, Hadith 139