Muharram is one of the four sacred months in Islam. It marks the beginning of the Islamic calendar. The 10th of Muharram is called Ashura.
On Ashura, the Prophet Musa (AS) and the Children of Israel were saved from Fir'aun (Pharaoh). The Prophet ﷺ fasted on this day and recommended Muslims to fast — preferably adding the 9th as well. He said: 'Fasting the day of Ashura, I hope Allah will expiate the sins of the previous year.'
Muharram is also a month for reflection on the sacrifices made for the preservation of Islam, particularly the tragedy of Karbala.