The Messenger of Allah (ﷺ) used to observe thirteen rak'ahs of the night prayer. Five out of them consisted of Witr, and he did not sit, but at the end (for salutation).
Sahih Muslim Book 6, Hadith 149
← Previous Hadith 'A'isha, the wife of the Messenger of Allah (ﷺ), said that between the time when the Messenger of Allah (ﷺ) finished the 'Isha' prayer which is called 'Atama by the people, he used to pray eleven rak'ahs, uttering the salutation at the end of every two rak'ahs, and observing the Witr with a single one. And when the Mu'adhdhin had finished the call (for the) dawn prayer and he saw the dawn clearly and the Mu'adhdhin had come to him, he stood up and prayed two short rak'ahs. Then he lay down on his right side till the Mu'adhdhin came to him for lqama. (This hadith has been narrated with the same chain of transmitters by Ibn Shihab, but in it no mention has been made of Iqama )

Sahih Muslim Book 6, Hadith 148 Next Hadith → This hadith has been narrated by Hisham with the same chain of transmitters.

Sahih Muslim Book 6, Hadith 150