It is Sunnah to fast the first nine days of Dhul-Hijjah, especially the day of `Arafah, for those who are not performing Hajj. This is confirmed by the following hadiths:
1. Abu Qatadah (may Allah be pleased with him) is reported to have said that the Prophet (peace and blessings be upon him) said: “Fasting on the day of `Arafah is an expiation for two years, the year preceding it and the year following it. Fasting the day of `Ashurah is an expiation for the year preceding it.” (Reported by “the group,” except for Al-Bukhari and At-Tirmidhi)
2. One of the wives of the Prophet (peace and blessings be upon him) said: “Allah’s Messenger used to fast the [first] nine days of Dhul-Hijjah, the day of `Ashurah, and three days of each month.”(Reported by Abu Dawud).
3. `Uqbah ibn`Aamr (may Allah be pleased with him) is reported to have said that the Messenger of Allah (peace and blessings be upon him) said: “The day of `Arafah [for those performing Hajj], the day of sacrifice, and the days of Tashreeq are `Eids (feasts) for us – the people of Islam – and they are days of eating and drinking.”
4- Abu Hurayrah (may Allah be pleased with him) narrates that the Prophet (peace and blessings be upon him) forbade fasting on the day of `Arafah for one who is actually at `Arafah.” (Reported by Ahmad, Abu Dawud, An-Nasa’i, and Ibn Majah).