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Narrated 'Aisha: (The tribe of) Quraish used to fast on the day of Ashura' in the Pre-lslamic period, and then Allah's Apostle ordered (Muslims) to fast on it till the fasting in the month of Ramadan was prescribed; whereupon the Prophet said, "He who wants to fast (on 'Ashura') may fast, and he who does not want to fast may not fast."