بُلُوغُ الْمَرَامِ
Bulugh al-Maram 389
The Book of Prayer
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] .
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].
Sunnah.com reference: Book 2, Hadith 293