Musnad Ahmad 1153:671

Muhammad ibn Ja'far narrated to us, he said: Shu'bah narrated to us, from Budayl, from Abdullah ibn Shaqiq, he said: I was ill in Persia, so I used to pray while sitting. I asked Aisha about that, and she said: "The Messenger of Allah (peace and blessings of Allah be upon him) used to pray for a long night standing, and for a long night sitting. So when he recited while standing, he would bow or humble himself while standing, and when he recited while sitting, he would bow while sitting."