I heard the Messenger of Allah (ﷺ) say: The witr is a duty, so he who does not observe it does not belong to us; the witr is a duty, so he who does not observe it does not belong to us; the witr is a duty, so he who does not observe it does not belong to us.
Sunan Abi Dawud Book 8, Hadith 4
← Previous Hadith The Messenger of Allah (ﷺ) came out to us and said: Allah the Exalted has given you an extra prayer which is better for you then the red camels (i.e. high breed camels). This is the witr which Allah has appointed for you between the night prayer and the daybreak.

Sunan Abi Dawud Book 8, Hadith 3 Next Hadith → Ibn Muhayriz said: A man from Banu Kinanah, named al-Makhdaji, heard a person called AbuMuhammad in Syria, saying: The witr is a duty (wajib).

Al-Makhdaji said: So I went to Ubadah ibn as-Samit and informed him.

Ubadah said: AbuMuhammad told a lie. I heard the Messenger of Allah (ﷺ) say: There are five prayers which Allah has prescribed on His servants. If anyone offers them, not losing any of them, and not treating them lightly, Allah guarantees that He will admit him to Paradise. If anyone does not offer them, Allah does not take any responsibility for such a person. He may either punish him or admit him to Paradise.

Sunan Abi Dawud Book 8, Hadith 5