This is what gives so much importance to the Day of Arafat in Islam

“The best supplication is that which is made on the day of ‘Arafāt. The best of it is what was said by myself and the prophets before me: There is no god but Allah alone without any partners, unto him belong the dominion and all praise and he has power over all things.” (Tirmidhī 3585)
 
The magnificent day of Arafat falls on the 9th of Dhul-Hajjah – the second day of Hajj. It serves as the climax of the annual pilgrimage (Hajj) in Islam.
 
After the sunrise on this blessed day, millions of pilgrims set out for the plain of Arafat, also known as Mount Arafat, located just outside the city of Mecca. It is on this very site where our beloved Holy Prophet (peace be upon him) delivered his farewell sermon for his ummah. The whole Day of Arafat, from dawn till dusk, is spent in devoted supplication, worship, prayers and seeking of Allah’s (SWT) forgiveness. It is a day of unlimited blessings and forgiveness.
 
In order to understand the significance of this day, some light needs to be shed on the virtues of this day and why it holds such a precious place in the heart of Islam.
 
Religion was perfected on this day
 

It was on the Day of Arafat when Allah (SWT) completed and perfected the religion of Islam, thereby fulfilling His favor upon His people. This day commemorates the finality of Divine revelation. According to Islamic tradition:
 
Reported by Tariq bin Shibab: Some Jews said, “Had this Verse been revealed to us, we would have taken that day as ‘eid (festival).” `Umar said, “What Verse?” They said:– 
 
“This day I have Perfected your religion for you, Completed My Favor upon you And have chosen for you Islam as your religion” (Quran 5.3)
 
 `Umar said, “I know the place where it was revealed; It was revealed while Allah’s Apostle was staying at `Arafat.” (Sahih Bukhari 5:59:689)
 
A day of gratitude

The Day of Arafat is considered a day of “Eid” and celebration for Muslims. It is an auspicious event of gratitude, reward, and piety. According to the Holy Prophet (peace be upon him):
 
Reported by Uqbah bin Amir: He said: “The Day of Arafah, the Day of Nahr, and the Days of Tashriq are Eid for us. The people of Islam, and they are days of eating and drinking,” (Tirmidhi 4:92)
 
And in another hadith:
 
Narrated by Uqbah bin Amir, the Prophet (peace be upon him) said: “The day of Arafat and the day of sacrifice and the day of At-Tashriq are Eid (festival) for us, the people of Islam, and they are days of eating and drinking.” (Abu Dawood 13:2413)
 
Day of forgiveness

If one fast on the Day of Arafat, the sins one has committed in the previous year and the year to come, are forgiven. In short, one earns a clean slate. It is ‘Sunnah’ of the Prophet (peace be upon him) to fast on this day. According to a hadith:
 
Reported by Abu Qutaadah: the Messenger of Allah (peace be upon him) was asked about fasting on the day of ‘Arafa (9th of Dhu’I-Hijja), whereupon he said: ‘It expiates the sins of the preceding year and the coming year.’”(Sahih Muslim 6:2603)
 
However, fasting on this day is only directed towards the non-pilgrims – the pilgrims are not required to fast on the Day of Arafat because the Prophet (peace be upon him) did not fast on this day in Arafat.
 
Protection from hell-fire

The Day of Arafat is an unmatched opportunity to gain eternal protection from the Hellfire and to earn forgiveness for all sins. It is a day when Allah (SWT) professes His pride in His creation that is standing at Arafat to His angels. According to Aisha (RA), the Holy Prophet (peace be upon him) said:
 
“There is no day when God sets free more servants from Hell than the Day of ‘Arafa. He draws near, then praises them to the angels, saying: What do these want?” (Sahih Muslim 7:3126)
 
Integral part of Hajj

Standing on Mount Arafat is an integral part of the annual pilgrimage; without it, Hajj cannot be complete. The Holy Prophet (peace be upon him) emphasizes its importance in another hadith narrated by Abdur-Rahman bin Yamar:
 
"The Hajj is 'Arafat, the Hajj is 'Arafat, the Hajj is 'Arafat. The days of Mina are three: But whoever hastens to leave in two days, there is no sin on him, and whoever stays on, there is no sin on him (2:203). And whoever sees (attends) the 'Arafah before the rising of Fajr, then he has performed the Hajj." (Tirmidhi 5:44:2975)
 
Such is the magnificence and significance of the blessed Day of Arafat in Islam.