Sunan Abi Dawud Book 5, Hadith 109
He (the Prophet) got up and prayed eight rak'ahs in pairs, and then observed witr with five rak'ahs and he did not sit between them.
I spent a night in the house of my maternal aunt Maimunah, daughter of al-Harith. The Prophet (ﷺ) 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 at 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.
The Messenger of Allah (ﷺ) used to pray thirteen rak'ahs, observing six rak'ahs in pairs including the two rak'ahs of dawn prayer. He would observe witr and five rak'ahs. He sat only in the last of them.