بسم االلهالرحمن اارحيم
Shaum (Arabic: صوم, transliteration: Sauwm) language means to hold or prevent. According to Shari'a Islam means to refrain from eating and drinking and all actions that can break the fast, starting from sunrise dawn sun, with certain conditions, to increase the piety of a Muslim. Fasting 'Arafat is fasting on the Day of Arafah, ie from the month of Dhu al-Hijjah. Fasting is highly recommended for Muslims who do not go Hajj, because as it is said in so many hadiths, fasting 'can erase sin for two years. The Day of Arafat is the day when God perfects Islam and perfected His favor at that time. The day of'Arafah is Akbar's day of pilgrimage by the majority of the salaf. The Day of Arafat is also a special day for this people.
Anas bin Malik once said, "Arafat Day is more than 10,000 other days." [1]. Anyone who fasts when it will get the forgiveness of sins (ie small sins) for two years.
Regarding the day of'Arafah, the Prophet sallallaahu 'alaihi wa sallam said,
ما من يوم أكثر من أن يعتق الله فيه عبدا من النار من يوم عرفة وإنه الملائكة فيقول ما أراد هؤلاء
"Among the days that God frees a lot of people from hell is the day of'Arafah. He will approach them and will reveal their virtue to the angels. Then Allah says: What do they want? "[2].
Ibn Rajab al-Hambali said, "The day of'Arafah is the day of liberation from the fires of hell. On that day, God will free anyone who is standing in Arafat and the inhabitants of the Muslim lands who do not observe. Therefore, the day after the day of'Arafah - that is the day of Eid al-Adha - is a day of'ed for the Muslims around the world. Neither one who performs the pilgrimage and who does not exercise it will obtain liberation from hellfire and forgiveness on the day of'Arafah. "[3]
Source:
Jurisprudence Sunnah 3, Sayyid Saabiq.
Moslemsunnah.wordpress.com, has been edited for alignment.
http://muslim.or.id/tazkiyatun-nufus/sebab-mendapatkan-ampunan-di-hari-arafah.html
[1] Latho-if Al Ma'arif, Ibn Rajab Al Hambali, p. 489, Al Maktab Al Islamiy, the first print, in 1428 H.
[2] HR. Muslim no. 1348, from 'A'ishah.
[3] Latho-if Al Ma'arif, Ibn Rajab Al Hambali, p. 482.