I heard the Messenger of Allah ﷺ say, "Witr is a duty, so whoever does not pray witr is not one of us. Witr is a duty, so whoever does not pray witr is not one of us. Witr is a duty, so whoever does not pray witr is not one of us."
حدثنا ابن المثنى حدثنا أبو إسحق الطالقاني حدثنا الفضل بن موسى عن عبيد الله بن عبد الله العتكي
سمعت رسول الله ﷺ يقول الوتر حق فمن لم يوتر فليس منا الوتر حق فمن لم يوتر فليس منا الوتر حق فمن لم يوتر فليس منا
[Daif] Ahmad reported it, 5/357, from the hadith of Fadl bin Musa via this route, and Hakim graded it sahih, 1/305, 306. Abu Muneeb Ubaydullah Ataki is hasan al-hadith except in what has been criticized of him, and this hadith is among what has been criticized of him.