Abu Dawud Book 2, Hadith Number 1246.
Narated By Abd Allah b. Shaqiq : I asked ‘Aisha about the voluntary prayers offered by the Apostle of Allah (PBUH). She replied: Before the noon prayer he would pray four rak’ahs in my house, them go out and lead the people in prayer, then return to my house and pray two rak’ahs. He would lead the people in the sunset prayer, then return to my house and pray two rak’ahs. Then he would lead the people in the night prayer, and enter my house and pray two rak’ahs. He would pray nine rak’ahs during the night, including witr (prayer). At night he would pray for a long time standing and a long time sitting. When he recited the Qur’an while standing, he would bow and prostrate himself from the standing position; and when he recited while sitting, he would bow and prostrate himself in the sitting position; and when dawn came he prayed two rak’ahs, and then he would come out and lead the people in the dawn prayer.