Al-Muwatta de Malik, 270

Un homme demanda à Abdallah Ibn Omar au sujet de la raka't impaire; est-elle obligatoire»? Il lui répondit: «L'Envoyé d'Allah (salallahou alayhi wa salam) r (Sur lui la grâce et la paix d'Allah) l'a faite ainsi que les musulmans». Comme l'homme insista sur la question, Abdallah lui donna la même réponse»

Yahya related to me from Malik that he had heard that a man asked Abdullah ibn Umar whether the witr was obligatory and Abdullah ibn Umar said, "The Messenger of Allah, may Allah bless him and grant him peace, prayed witr, and the muslims prayed witr." The man began repeating his question, and Abdullah ibn Umar kept saying, "The Messenger of Allah, may Allah bless him and grant him peace, prayed witr, and the muslims prayed witr