Musnad Ahmad 1153:1541

'Abd al-Malik ibn 'Amr narrated to us, he said: Yazid narrated to us, he said: Hisham informed us, from Yahya, from Abu Salamah, he said: I asked 'Aishah about the prayer of the Messenger of Allah, peace and blessings of Allah be upon him, at night? She said: He used to pray thirteen rak'ahs; he would pray eight rak'ahs, then he would perform witr, then he would pray two rak'ahs while he was sitting. When he wanted to bow, he would stand up and then bow. And he would pray the two rak'ahs between the call to prayer (adhan) and the iqamah of the morning prayer.