It wasnarrated that Ibn 'Umar said:
"The Messenger of Allah (ﷺ)usedto pray (voluntary prayers) at night two by two, and he wouldprayone Rak'ah of Witr." (ES)
English reference (ES): Vol. 1, Book 5, Hadith 1174 (ES)
Arabic reference (ES): Book 5, Hadith 1230 (ES)