Musnad Ahmad 1153:1839

Hajjaj narrated to us, he said: Layth narrated to us, he said: Yazid ibn Abi Habib narrated to me, from Ja'far ibn Rabi'ah, from Abu Salamah, that he heard 'Aishah saying: The Prophet of Allah, peace and blessings of Allah be upon him, used to pray every night thirteen rak'ahs: nine while standing, and two while he was sitting. Then he would wait until the first call for the dawn prayer was made, then he would pray two rak'ahs.