Ali said:
"Al-Witr is not incumbent like your obligatory prayers, but it is a Sunnah of Allah's Messenger (ﷺ) who said: "Indeed Allah is Witr (One), and He loves Al-Witr, so perform Al-Witr O people of the Qur'an."
Sufyan Ath-Thawri and others reported from Abu Ishaq, from Asim bin Damrah, that :
Ali said: "Al-Witr is not incumbent like the status of the obligatory prayers, but it is a Sunnah which Allah's Messenger (ﷺ) practiced."