"Allah's Messenger ordered me to perform Al-Witr before sleeping."
Jami` at-Tirmidhi Book 3, Hadith 4
← Previous Hadith Ali said: "Al-Witr is not incumbent like the status of the obligatory prayers, but it is a Sunnah which Allah's Messenger practiced."

Jami` at-Tirmidhi Book 3, Hadith 3 Next Hadith → he asked Aishah about the Witr of the Prophet. She said: "He would perform Witr during all of the night; (either) its beginning, its middle, or its end. So when he died, his Witr ended, during the approachof As-Sahar."

Jami` at-Tirmidhi Book 3, Hadith 5