´It was narrated that Ali, may Allah (SWT) be pleased with him, said:` "Witr is not essential like the obligatory prayers, but it is the sunnah of the Messenger of Allah (ﷺ)."
Hadith ReferenceSunan an-Nasa'i / The Book of Qiyam Al-Lail (The Night Prayer) and Voluntary Prayers During the Day / Hadith: 1677