The Prophet ﷺ said, "Witr is a duty. Whoever wishes may pray witr with seven, whoever wishes may pray it with five, whoever wishes may pray it with three, and whoever wishes may pray it with one."
أخبرنا عمرو بن عثمان قال حدثنا بقية قال حدثني ضبارة بن أبي السليل قال حدثني دويد بن نافع قال أخبرني ابن شهاب قال حدثني عطاء بن يزيد
أن النبي ﷺ قال الوتر حق فمن شاء أوتر بسبع ومن شاء أوتر بخمس ومن شاء أوتر بثلاث ومن شاء أوتر بواحدة
[Sahih] Reported by Abu Dawud, Prayer, chapter on the number of units of Witr, no. 1422, and Ibn Majah, Establishing Prayers, chapter on what has been said about Witr being three, five, seven, or nine units, no. 1190, from the hadith of Ibn Shihab Zuhri, with this same chain. It is also found in al-Kubra, no. 442. Ibn Hibban, Hakim, Dhahabi and others graded it sahih, and the hadith is sahih whether reported as raised (marfu) or as a companion's statement (mawquf).Ata bin Yazid is al-Laythi.