´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 practiced."
Related hadith on this topic
Explanation & Benefits
Hafiz Muhammad Ameen
1677. Commentary: Since Witr is a Sunnah of the Messenger of Allah (sallallahu alayhi wa sallam), which he never abandoned, therefore it is not permissible to abandon it without a valid excuse.
Source: Sunan Nasa'i: Translation and Benefits by Shaykh Hafiz Muhammad Amin Hafizullah, Page: 1677