Musnad Ahmad 1153:1430

I read to Abd al-Rahman: Malik, from Hisham ibn Urwah, from his father, from Aisha, the wife of the Prophet, may Allah bless him and grant him peace, that she informed him: "She did not see the Messenger of Allah, may Allah bless him and grant him peace, pray the night prayer sitting until he grew old. He would recite while sitting, and when he intended to bow, he would stand up and recite about thirty or forty verses, then he would bow."