The Messenger of Allah ﷺ said, "The witr is a single rakah at the end of the night."
قال رسول الله ﷺ: الوتر ركعة من آخر الليل.
Muslim narrated it in the chapter on the prayer of travelers (752) from Shayban bin Farroukh, who said, Abdul-Warith narrated to us, from Abu Tayah, who said, Abu Majliz narrated to me, from Ibn Umar, and he mentioned it. Shuba also narrated it, from Qatada, from Abu Majliz, with the same wording.Muawiya performed witr after Isha with one rakat, and a freed servant of Ibn Abbas was present with him. So he went to Ibn Abbas, who said, "Leave him alone, for he accompanied the Messenger of Allah ﷺ."In another version, it was said to Ibn Abbas, "What do you say about the Commander of the Faithful, Muawiya, for he performed witr with only one rakat?" He said, "He is a jurist."Bukhari narrated it in the chapter on the virtues of the companions of the Prophet ﷺ (3765, 3764) through two routes from Ibn Abu Mulayka, who said, "Muawiya performed witr," and he mentioned it.