The Messenger of Allah (ﷺ) used to pray thirteen rak'ahs during the night, observing a witr out of that with five, he did not sit during the five except the last and then gave the salutation.

Abu Dawud said: Ibn Numair reported it from Hisham recently.
Sunan Abi Dawud Book 5, Hadith 89
← Previous Hadith He would observe witr with a single rak'ah and make a prostration as long as you would take to recite fifty verses before raising his head. When the mu'adhdhin finished his call for the dawn prayer and the dawn became clear to him.... Then the narrator transmitted the rest of the tradition to the same effect.

Some narrators added something more in their version.

Sunan Abi Dawud Book 5, Hadith 88 Next Hadith → The Messenger of Allah (ﷺ) used to pray thirteen rak'ahs during the night ; he then offered two light rak'ahs of prayer when he heard the call to the dawn prayer.

Sunan Abi Dawud Book 5, Hadith 90