It is narrated from Hazrat Abu Qatadah (may Allah be pleased with him) that a person asked the Holy Prophet (peace and blessings be upon him) about fasting on the Day of Arafah (9th of Dhul-Hijjah), so the Holy Prophet (peace and blessings be upon him) said: "It is an expiation for two years." Then someone asked about fasting on the Day of Ashura, so he said: "It is an expiation for one year."