Fasting on the Day of Ashura

Fasting on Muharram 10, known as the Day of ‘Ashura’, expiates for the sins of the past year. When the Prophet (peace and blessings be upon him) arrived in Madinah in 622 CE, he found that the Jews there fasted on Muharram 10 and asked them the reason for their fasting on this day. They said,” This is a blessed day. On this day Allah saved the Children of Israel from their enemy (in Egypt) and so Prophet Musa [Moses] fasted on this day giving thanks to Allah.”
The Prophet (peace and blessings be upon him) said,
“We are closer to Musa than you are.”
He fasted on that day and commanded Muslims to fast on this day. (Al-Bukhari). Ibn ‘Abbas reported: The Messenger of Allah fasted on the day of ‘Ashura’ and ordered the people to fast on it. According to scholars, you may choose to fast ‘Ashura’ on (ninth, tenth, and eleventh); two days or one day only (the tenth). The Prophet said, “Fasting the day of ‘Ashura’ is of great merit. I hope that Allah will accept it as an expiation for the sins committed in the previous year.” (Muslim)