The Book Pertaining to the Excellent Qualities of the Holy Prophet (may Peace be upon them) and His Companions (Kitab Al-Fada'il)

Muslim :: Book 30 : Hadith 5821

Amir b. Sa'd reported on the authority of his father that Allah's Messenger (may peace be upon him) said: The greatest sinner amongst the Muslims is one who asked about a thing (from Allah's Apostle) which had not been forbidden for the Muslims and it was forbidden for them because of his persistently asking about it.

Source materials are from the University of Southern California MSA site
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