Significance & Virtues of the Day of Arafah

Fasting on the day of Arafah is an expiation for TWO years:

The ninth day of Dhul-Hijjah is the day of ’Arafah, since it is on this day that the pilgrims gather at the mountain plain of ’Arafah, praying and supplicating to their Lord. It is mustahabb (highly recommended) for those who are not pilgrims to fast on this day, since the Prophet صلّى اللَّهُ عليه وسلّم was asked about fasting on the day of ’Arafah, so he said,

“It expiates the sins (Minor) of the past year and the coming year.”

[Muslim (no. 1162)]

Imaam at-Tirmidhee رحمه الله said,

“The People of Knowledge consider it recommended to fast on the day of ’Arafah, except for those at ’Arafah.”

[Muslim (no. 1348)]

Allaah frees slaves from the fire on Arafat more than any other day

Likewise, the Prophet صلّى اللَّهُ عليه وسلّم said,

‘There is no day on which Allaah frees people from the Fire more so than on the day of ’Arafah. He comes close to those (people standing on ’Arafah), and then He revels before His Angels saying, ‘What are these people seeking.”

[Jaami’ut-Tirmidhee (3/377)]

Forgiveness of the Sins even if they are like the foam on the Sea

As for you staying till the evening in Arafah, then Allaah descends to the sky of the Dunya and He boasts about you to the Angels, and says:
 

‘My slaves have come to Me, looking rough, from every deep valley hoping for My mercy, so if your sins were equivalent to the amount of sand or the drops of rain or like the foam on the sea I will forgive them. So go forth My slaves! Having forgiveness and for what or who you have interceded for.’

[Reported by at-Tabarani in his book “al-Kabeer” and by al-Bazaar. Shaykh Al-Albani graded it Hassan. Taken from ‘Saheeh al-Targheeb wa Tarheeb’. Volume 2, Page 9-10, hadeeth no. 1112]

 (Taken from 'Saheeh al-Targheeb wa Tarheeb' By the Shaykh Muhammad Nasr ud-Deen al-Albaani)

It is the day on which the religion was perfected and Allaah’s Favour was completed.

In Al-Saheehayn it was reported from ‘Umar ibn al-Khattaab رضي اللّه عنـه that a Jewish man said to him,

“O Ameer al-Mu’mineen, there is an aayah in your Book which you recite; if it had come to us Jews, we would have taken that day as an ‘Eid (festival).” ‘Umar said, “Which aayah?” He said: “This day I have perfected your religion for you, completed My favour upon you, and have chosen for you Islam as your religion.” (al-Maa’idah 5:3). 

‘Umar said,

“We know on which day and in which place that was revealed to the Prophet (peace and blessings of Allaah be upon him). It was when he was standing in ‘Arafaah on a Friday.”

Allaah expresses His pride to His angels

It was reported from Ibn ‘Umar that the Prophet صلّى اللَّهُ عليه وسلّم said:

“Allaah expresses His pride to His angels at the time of ‘Ishaa’ on the Day of ‘Arafaah, about the people of ‘Arafaah. He says, ‘Look at My slaves who have come unkempt and dusty.’”

(Narrated by Ahmad and classed as saheeh by al-Albaani.)

The standing on ‘Arafaat is the hajj

The standing on ‘Arafaat is the hajj. The crowds should remind you of the Day of Resurrection. Humble yourself to Allaah, manifest your ‘uboodiyyah to Him Alone through du’aa, sincere intention and strong determination to free yourself from the sins of the past and to build up a commitment to rush for doing what is good. Think of becoming a better person when you return. Rid yourself of false pride and showing off because it may ruin what you gain on this day.

[Source : Hajj and Tawheed by Dr. Saleh as-Saleh]