Abu Sa‘īd al-Khudri (may Allah be pleased with him) reported the Prophet (may Allah's peace and blessings be upon him) said: "If anyone sleeps before praying Witr or forgets it, let him pray it once he remembers it." Authentic hadith - Narrated by Ibn Majah - Narrated by At-Termedhy - Narrated by Abu Daoud - Narrated by Ahmad