Abu Dawud Book 2, Hadith Number 1352.
Chapter : On the number of rakahs of the prayer at night.
Narated By Ibn ‘Abbas : I spent a night in the house of my maternal aunt Maimunah, daughter of al-Harith. The Prophet (PBUH) offered the night prayer. He then came and prayed four rak’ahs and slept. He then stood up and prayed. I stood at his left side. He made me go round and made me stand on his right side. He then prayed five rak’ahs and slept, and I heard his snoring. He then got up and prayed two rak’ahs. Afterwards he came out and offered the dawn prayer.