Musnad Ahmad 1153:1801

Isma'il narrated to us, he said: Khalid informed us, from Abdullah ibn Shaqiq, he said: I asked Aisha about the prayer of the Messenger of Allah (peace and blessings of Allah be upon him). She said: "He used to pray four before Dhuhr, and two after it, and two before Asr, and two after Maghrib, and two after Isha. Then he would pray nine at night." I said: "Standing or sitting?" She said: "He would pray a long night standing, and a long night sitting." I said: "What does he do when he is standing? And what does he do when he is sitting?" She said: "When he recited standing, he would bow standing, and when he recited sitting, he would bow sitting. And two rak'ahs before the morning prayer."