Sayyiduna Abu Qatadah Ansari (may Allah be pleased with him) narrates: The Noble Prophet (peace and blessings be upon him) said: Fasting on the day of Arafah becomes an expiation for the sins of this year and the following year, and fasting on the day of Ashura becomes an expiation for the sins of one year. Sufyan says: The narrator named Dawud has reported this, Ata used not to fast on this day, until this hadith reached him (and after that he started fasting on this day).