The Book of Prayers (Kitab Al-Salat)
Muslim :: Book 4 : Hadith 1531
Abu Huraira reported the Apostle of Allah (may peace be upon him) as saying: When the prayer commences then there is no prayer (valid), but the obligatory prayer. This hadith has been narrated by Warqa' with the same chain of transmitters.
Source materials are from the University of Southern California MSA site|
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