Ashura, observed on the 10th of Muharram (with the 9th, called Tasu’a, observed alongside it), is one of the most meritorious voluntary fasts in the Islamic calendar. The name comes from the Arabic word for “tenth” (‘ashr).

The Prophet Muhammad (peace be upon him) found the Jews of Madinah fasting on this day and asked them why. They answered that it was the day on which Allah saved Musa (Moses) and the Children of Israel from Pharaoh. The Prophet (peace be upon him) said: “We have more right to Musa than they do,” and he fasted that day and ordered the Muslims to fast it as well (Sahih al-Bukhari).

To distinguish the Muslim practice from that of the People of the Book, the Prophet (peace be upon him) later said: “If I live until next year, I will fast the ninth as well.” (Sahih Muslim). He passed away before the next Muharram, so the established Sunni practice is to fast both the 9th and 10th, or at minimum the 10th.

The reward for fasting Ashura is significant. The Prophet (peace be upon him) said: “Fasting the day of Ashura, I hope from Allah, expiates the sins of the previous year.” (Sahih Muslim). The Qur’an also references the sacred status of Muharram (Surah at-Tawbah 9:36).

Ashura is not Eid and is not a festival. It is a day of fasting, gratitude, and remembrance. Some communities also commemorate the martyrdom of Husayn ibn Ali at Karbala on this day; that practice is more central to Shia observance, while the Sunni emphasis remains on the fast tied to the deliverance of Musa.