Narrated [Abu Sa'id al-Khudri (RA)]:

Allah's Messenger (ﷺ) said: "Whoever oversleeps and misses the Witr, or forgets it, should pray (when he awakens) in the moming or when he remembers." [Reported by al-Khamsah except an-Nasa'i].

وَعَنْهُ قَالَ: قَالَ رَسُولُ اَللَّهِ ‏- صلى الله عليه وسلم ‏-{ مَنْ نَامَ عَنْ اَلْوِتْرِ أَوْ نَسِيَهُ فَلْيُصَلِّ إِذَا أَصْبَحَ أَوْ ذَكَرَ } رَوَاهُ اَلْخَمْسَةُ إِلَّا النَّسَائِيَّ .‏ [1]‏ .‏