The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 1643
Abu Mijlaz reported: I asked Ibn 'Abbas about the Witr prayer. He said: I heard the Messenger of Allah (may peace be upon him) as saying: It is a rak'ah at the end of the night prayer.
Source materials are from the University of Southern California MSA site|
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