Musnad Ahmad 1153:266

Yahya narrated to us, from Muhammad ibn ‘Amr, who said: Abu Salamah narrated to me, saying: I said to ‘Aishah: "O my mother, how was the prayer of the Messenger of Allah (peace and blessings of Allah be upon him) after the final night prayer (al-‘isha’ al-akhirah)?" She said: "Nine [rak'ahs] standing, and two sitting, and two after the two calls [to prayer]."