From Sahih Muslim (Hadith 1707):
Alqama b. Waqqas reported: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
Reference: Muslim 1707