According to the Prophet Muhamamad, peace be upon him, the first ten days of this month are a special time for devotion. During these days, preparations are underway for those who are undertaking the pilgrimage, and most of the actual pilgrimage rites occur. In particular, the 9th day of the month marks the Day of Arafat, and the 10th day of the month marks the Eid al-Adha (Festival of Sacrifice). Even for those who are not traveling for the pilgrimage, this is a special time to remember Allah and spend extra time in devotion and good deeds.
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