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."
Muwatta Malik Book 7, Hadith 17