Muwatta Malik Book 7, Hadith 22
Yahya related to me from Malik from Abdullah ibn Dinar that
Abdullah ibn Umar used to say, "The maghrib prayer is the witr of the
daytime prayers."
Malik said, "If someone prays witr at the
beginning of the night, and goes to sleep, and then wakes up and it
seems good to him to pray, let him pray, two rakas at a time. That is
what I like most of what I have heard."
Yahya related to me from Malik from Ibn Shihab that Sad ibn Abi Waqqas used to pray witr after isha with one raka.
Malik said, "This is not the situation with us. Rather three is the minimum for witr."
Yahya related to me from Malik from Abd al Karim ibn Abi'l-Mukhariq al-Basri from Said ibn Jubayr that Abdullah ibn Abbas slept, and when he woke up, he said to his servant, "Go and see what the people have done," (by that time his sight had gone.) The servant went out and returned saying, "The people have left from subh," so Abdullah ibn Abbas got up and prayed witr and then prayed subh.