عن علي رضي الله عنه
قال: الوتر ليس بختم كصلاة المكتوبة ولكن سن رسول الله صلى الله عليه وسلم قال: «إن الله وتر يحب الوتر، فأوتروا يا أهل القرآن»
The Witr prayer is not obligatory as the prescribed Salat (prayers), but the Messenger of Allah (sallallahu alayhi wa sallam) observed it as his regular practice (Sunnah). He (sallallahu alayhi wa sallam) said, “Allah is Witr (single, odd) and loves what is Witr. So perform Witr prayer. O followers of Qur’an, observe Witr (prayer).”.
Riyad as-Salihin 1132, Book 9, The Book of Virtues, Hadith 142. 1 min read