What did the Prophet Muhammad (saw) say regarding the observance of fasting on the day of Ashura?
 Narrated `Aisha:                     The people used to fast on 'Ashura (the tenth day of the month of Muharram) before the fasting of Ramadan was made obligatory. And on that day the Ka`ba used to be covered with a cover. When Allah made the fasting of the month of Ramadan compulsory, Allah's Apostle said, "Whoever wishes to fast (on the day of 'Ashura') may do so; and whoever wishes to leave it can do so."