Abu Dawud Book 2, Hadith Number 1415.

Chapter : On a person who does not observe the witr prayer.

Narated By Ubadah ibn as-Samit : 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 Apostle of Allah (PBUH) 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.