(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 prayer. (TR)
Reference (TR): Sahih Muslim 752 a (TR)
In-book reference (TR): Book 6, Hadith 186 (TR)
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1641 (TR)