Fast on the Day of 'Ashurah'.

The hadith reported by Ibn Abbas states that the Messenger of Allah commanded Muslims to fast on the day of ‘Ashura’. This is a significant day in Islamic history as it marks many important events such as when Moses and his people were saved from Pharaoh and when God accepted Adam's repentance. Therefore, fasting on this day is seen as an act of gratitude for these blessings. It also serves as a reminder to stay away from sins and strive for righteousness. Additionally, it teaches us about self-discipline and patience which are essential qualities for any believer.