What was the pre-islamic practice of the tribe of Quraish regarding the day of Ashura and how did the Prophet Muhammad (saw) respond to it upon his migration to Medina?
 Narrated `Aisha:                     'Ashura' (i.e. the tenth of Muharram) was a day on which the tribe of Quraish used to fast in the prelslamic period of ignorance. The Prophet also used to fast on this day. So when he migrated to Medina, he fasted on it and ordered (the Muslims) to fast on it. When the fasting of Ramadan was enjoined, it became optional for the people to fast or not to fast on the day of Ashura.