Sayyiduna Amr bin al-As (may Allah be pleased with him) said: A man from among the Companions of the Messenger of Allah (peace and blessings be upon him) told me that he heard the Messenger of Allah (peace and blessings be upon him) say: "Allah, the Mighty and Majestic, has granted you an additional prayer, so pray it between the Isha prayer and the Fajr prayer: the witr, the witr." Indeed, that Companion was Abu Basrah al-Ghifari (may Allah be pleased with him).
Abu Tamim said: Abu Dharr (may Allah be pleased with him) and I were sitting, and Abu Dharr (may Allah be pleased with him) took me by the hand and we went to Abu Basrah (may Allah be pleased with him). We found him at the door near the house of Amr, and Abu Dharr (may Allah be pleased with him) said to him: "O Abu Basrah! Did you hear the Messenger of Allah (peace and blessings be upon him) say: 'Allah has granted you an additional prayer, so pray it between Isha and the Fajr prayer: the witr, the witr'?" He said: "Yes." Abu Dharr (may Allah be pleased with him) asked: "Did you hear it yourself?" He said: "Yes."
Hadith Referenceالمعجم الكبير للطبراني / باب الجيم / 2154