(20) باب صَلاَةُ اللَّيْلِ مَثْنَى مَثْنَى وَالْوِتْرُ رَكْعَةٌ مِنْ آخِرِ اللَّيْلِ
Ibn Umar reported Allah's Messenger (ﷺ) as saying:
Witr is a rak'ah at the end of the night prayer. (TR)
Reference (TR): Sahih Muslim 752 b (TR)
In-book reference (TR): Book 6, Hadith 187 (TR)
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1642 (TR)