Fasting ʿĀshūrāʾ expiates the previous year. The Prophet ﷺ said: “Fasting the Day of ʿĀshūrāʾ — I hope from Allah that it expiates the year before it.” (Muslim). It is the day Allah saved Mūsā and drowned Firʿawn; the Prophet ﷺ fasted it and said: “I have more right to Mūsā than you.” (al-Bukhārī).
العربية: عن أبي قتادة رضي الله عنه أنّ النبيّ ﷺ قال: «صيامُ يوم عاشوراء أحتسبُ على الله أن يُكفّر السنة التي قبله». (مسلم).
Fast the 10th of Muḥarram — a year of sins wiped away.