Hadith 8:179
Ibn 'Umar (May Allah be pleased with them) reported:
The Prophet (ﷺ) performed the night prayer in pairs (i.e., Rak'ah) and made it odd number by observing one Rak'ah (as Witr). [Al-Bukhari and Muslim] .
وعنه قال: كان النبي صلى الله عليه وسلم ، يصلي من الليل مثنى مثنى، ويوتر بركعة. ((متفق عليه))