The Messenger of Allah (may Allah bless him and grant him peace) said:
“The observance of three days’ fast every Month and that of Ramadan every year is a perpetual fasting. I seek from Allah that fasting on the day of ‘Arafa may atone for the sins of the preceding and the coming years. and I seek from Allah that fasting on the day of ‘Ashura may atone for the sins of the preceding year.”
[Taken from a longer hadith related in Sahih Muslim]
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