Ibn Buraydah narrates from his father (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Witr is a duty (haqq); whoever does not pray witr has no connection with us."
Al-Bukhari said: Ubaydullah bin Abdullah Abu al-Munib narrates from Ibn Buraydah, and Zayd bin al-Hubab heard from him; he has munkar (denounced) narrations. Abu Ahmad (Ibn Adi) said: In my view there is no harm in him, and Yahya bin Ma'in also declared him thiqah (trustworthy). And Allah knows best.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 4464