Regarding the Islamic ruling on fasting the day of Arafah for Muslims, a Muslim scholar and renowned Da`iyah, Sheikh `Abdel Khaliq Hasan Ash-Shareef, said:
“It is reprehensible (makruh) for pilgrims to fast on the Day of `Arafah. However, it is Sunnah for non-pilgrims to fast on that day. The Prophet (peace and blessings be upon him) encouraged Muslims who are not performing Hajj to fast on that day hoping that it expiates the sins of one immediate past year and he asked Allah to forgive sins of one coming year due to its fasting.
Elaborating more on this, we would like to cite what Sheikh Sayyed Sabiq, states in his well-known book, Fiqh As-Sunnah:
“It is confirmed that the Prophet (peace and blessings be upon him) did not fast on the Day of `Arafah. The Prophet (peace and blessings be upon him) said: “Verily the Day of `Arafah, the Day of Sacrifice (Yawm An-Nahr), and the days of Tashreeq (the 10th, 11th and 12th of Dhul-Hijjah) are our days of festivities. These are the days of eating and drinking.” (Sunan al-Nasa’i). It is also established that the Prophet (peace and blessings be upon him) forbade fasting on the Day of `Arafah for those who are at `Arafah (for pilgrimage).
Abu Hurairah, (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.” (Ahmad, Abu Dawud, An-Nasa’i, and Ibn Majah)
This has led most scholars to conclude that it is desirable not to fast on the Day of `Arafah, so that the pilgrim will be strong enough to devote himself wholeheartedly to worship and supplicating.
Some of the hadiths that encourage fasting on the Day of `Arafah are concerned with the people who are not staying at `Arafah as pilgrims performing Hajj.”