It wasnarrated from Abu Ayyub Al-Ansari that the Messenger of Allah(ﷺ)said:
"Witr is Haqq.* Whoever wishes let him pray Witr with five(Rak'ah), and whoever wishes let him pray Witr with three (Rak'ah),and whoever wishes let him pray Witr with one (Rak'ah)."
English reference: Vol. 1, Book 5, Hadith 1190
Arabic reference: Book 5, Hadith 1246