It is reported from the Prophet ﷺ that he rose during the night, cleaned his teeth with a siwak, then prayed two units. He then slept, rose again, cleaned his teeth, performed ablution, and prayed two units. He continued in this manner until he had prayed six units, then prayed three units of witr, and finally prayed two more units.
أخبرنا محمد بن رافع قال حدثنا معاوية بن هشام قال حدثنا سفيان عن حبيب بن أبي ثابت
عن النبي ﷺ أنه قام من الليل فاستن ثم صلى ركعتين ثم نام ثم قام فاستن ثم توضأ فصلى ركعتين حتى صلى ستا ثم أوتر بثلاث وصلى ركعتين
Muslim recorded it in Salat al-Musafirin, the chapter on the prayer and supplication of the Prophet ﷺ at night, h: 191/763, from the hadith of Habib, by this route. It is also in Kubra, h: 1344.