A man asked the Prophet (PBUH) about fasting on the Day of 'Arafah? The Prophet (PBUH) replied: I have the best expectation of Allah that he will expiate the previous year and the coming one. The man said: O Messenger of Allah, what about fasting on 'Ashura'? The Prophet (PBUH) replied: I have the best expectation of Allah that he will expiate the previous year.