Fasting on Day of Arafah and Ashura

Abu Hafsah, may Allah be pleased with him , reported that the Prophet, upon whom be peace , said:

“Fasting on the Day of 'Arafah absolves the sins for two years: the previous year and the coming year, and fasting on 'Ashura , (the tenth day of Muharram ) atones for the sins of previous years.”

Reported by all except Al-Bukhari and At-Tirmidhi