Musnad Ahmad 1153:1969

Yazid narrated to us, he said: Bahz bin Hakim narrated to us—and once he said: He informed us—he said: I heard Zurarah bin Awfa saying: Aisha was asked about the night prayer of the Messenger of Allah (ﷺ). She said: "He would pray the Isha, then pray two rak'ahs after it, then sleep. When he woke up, his ablution vessel would be covered and his siwak would be ready, so he would use the siwak, then perform ablution. Then he would stand and pray eight rak'ahs, reciting in them the Opening of the Book (Al-Fatiha) and whatever he wished of the Quran"—and once he said: "whatever Allah willed of the Quran." "He would not sit in any of them except in the eighth; he would sit in it, recite the tashahhud, then stand up and not perform the taslim. Then he would pray one rak'ah, then sit, recite the tashahhud, supplicate, and then perform one taslim: 'As-salamu 'alaykum,' raising his voice with it until he would wake us up. Then he would say 'Allahu Akbar' while sitting, recite, then bow and prostrate while sitting. He would pray two rak'ahs while sitting. This is eleven rak'ahs." "When his flesh increased and he became heavy, he made the nine into seven; he would not sit except as he sat in the first (instance), and he would pray the two rak'ahs while sitting. This was the prayer of the Messenger of Allah (ﷺ) until Allah took his soul."