Al-Aswad bin Hilal narrates: I bear witness that I heard Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) proclaiming it aloud: "The time of witr is between the two prayers, that is, between the later Isha, which you call al-Atamah, and the Fajr prayer. Whenever you pray witr, it is good."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9380