(20) باب صَلاَةُ اللَّيْلِ مَثْنَى مَثْنَى وَالْوِتْرُ رَكْعَةٌ مِنْ آخِرِ اللَّيْلِ
Abu Mijlaz reported:
I asked Ibn 'Abbas about the Witr prayer. He said: I heard the Messenger of Allah (ﷺ) as saying: It is a rak'ah at the end of the night prayer. (ID)
Reference (ID): Sahih Muslim 753 (ID)
In-book reference (ID): Book 6, Hadith 188 (ID)
USC-MSA web (English) reference(deprecated numbering scheme): Book 4, Hadith 1643 (ID)