The ninth of Dhul-Hijjah -
It's a great day of Arafat. Allah swore by the day of Arafat, which points to its greatness. Allah said: "And [by] the promised Day. And [by] the witness and what is witnessed". (The Holy Quran, Surah 85. "The Mansions Of The Stars, Constellations", verses 2-3) The Messenger of Allah (peace and blessings be upon him) said:
"The promised day is the Day of Resurrection, the witnessed day is the Day of Arafat, and the witnessing day is Friday". (Narrated by al-Tirmidhi and classed as saheeh by al-Albani)
On the day of Arafat Allah frees His servants from hell and forgive them their sins.
It was narrated that Aisha (may Allah be pleased with her) said: The Messenger of Allah (peace and blessings of Allaah be upon him) said:
"There is no day on which Allah ransoms more of His slaves from the Fire than the day of ‘Arafah. He draws close then He boasts about them before the angels and says, ‘What do these people want?'" (Narrated by Muslim 1348)
It was also narrated from Anas that the Prophet (peace and blessings be upon him) said on the day of Arafat: "'O Bilal! Ask the people to be quiet and listen to me.' Bilal stood up and asked the people to be quiet and listen to the Prophet (peace be upon him). When the people were quiet, the Prophet (peace be upon him) said: O People!
A little while ago Gabriel (peace be upon him) came to me. Gave me salutations from Allah, and informed me that Allah has forgiven those who spend the Day at Arafat, and those who stop at Mash'ar al-Haram, and that He has guaranteed their debts!'.At this 'Umar bin al-Khattab stood up and asked, 'O Allah's Messenger, is this for us only?' The Prophet (peace be upon him) said, "This is for you, and for all those who will come after you until the Day of Judgment'".
(Ibn al-Mubarak. Hadith authentic. See Saheeh al-Targib 2 / 33)
The best supplication (du'a) - is a supplication on the day of Arafat. Reported from Abdullah ibn Amr that the Messenger of Allah (peace and
blessings be upon him) said: "The best supplication is that of the Day of Arafat, and the best thing that I and other Prophets before me said, is: La ilaha illa allahu wahdahu la
sharika lah, lahu al-mulku wa lahu al-hamdu wa huwa `ala kulli shai'in qadeer (There is no god but Allah alone. He has no partners. To Him belong the sovereignty and all praise. He has power over all things)". (Al-Tirmidhi)
Hafiz Ibn Abdul-Barr said: "The indication in this hadith that supplicating on the Day of Arafat is better than supplicating on other days. And in this hadith there is also an indication that all the supplications or most of them on the Day of Arafat are answered. And also in this hadith indicated that the best remembrance of
Allah is saying "la ilaha illa-Allah". (See al-Tamhid 6/41-42). Imam al-Baji said: "The best of supplication is on the day of Arafat mean the dhikr with the greatest blessing, the greatest reward and that which is most likely to be
answered. It may be interpreted as referring to pilgrims only, because the meaning of supplication on the day of Arafat is very true in their case, and applies especially to them. But if the day of Arafat is regarded in general terms, it is described as such because of the pilgrims being there. And Allah knows best". (See Sharh al-Muwatta 1/358).
It is proven that some of the salaf regarded "al-ta'reef" as permissible, which means gathering in the mosques to offer du'aa' (supplication) and remember Allah (dhikr) on the day of Arafat.
***
What are the virtues of the Day of Arafat?
Praise be to Allah.
1. It is the day on which the religion was perfected and Allah's Favour was completed.
In Al-Saheehayn it was reported from ‘Umar ibn al-Khattaab (may Allah be pleased with him) that a Jewish man said to him, "O Ameer al-Mu'mineen, there is an ayah 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 ayah?" 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." [The Holy Quran, Surah 5."The Table Spread", verse 3]. ‘
Umar said, "We know on which day and in which place that was revealed to the Prophet (peace and blessings of Allah be upon him). It was when he was standing in Arafat on a Friday."
2. It is a day of Eid for the people who are in that place.
The Prophet (peace and blessings of Allah be upon him) said: "Yawm Arafat (the day of Arafat), Yawm al-Nahr (the Day of Sacrifice) and
Ayyaam al-Tashreeq (the 3 days following Yawm al-Nahr) are Eid (festival) for us, the people of Islam. These are days of eating and drinking".
This was narrated by the authors of al-Sunan.
It was reported that ‘Umar ibn al-Khattaab said:
"It - i.e., the ayah ‘This day I have perfected...' was revealed on a Friday, the Day of Arafat, both of which - praise be to Allah - are Eids for us."
3. It is a day by which Allah swore an oath.
The Almighty cannot swear by anything except that which is mighty. Yawm Arafat is the "witnessed day" mentioned in the ayah (interpretation of the meaning): "By the witnessing day [Friday] and by the witnessed day [the Day of Arafat]."
(The Holy Quran, Surah 85. "The Mansions Of The Stars, Constellations", verse 3)
It was reported from Abu Hurayrah (may Allah be pleased with him) that the Prophet (peace and blessings of Allah be upon him) said: "The promised day is the Day of Resurrection, the witnessed day is the Day of Arafat, and the witnessing day is Friday".
(Narrated by al-Tirmidhi and classed as saheeh by al-Albani).
It is the "odd" [i.e., odd-numbered, Witr] by which Allah swore in the ayah
(interpretation of the meaning):
"And by the even and the odd". (The Holy Quran, Surah 89. "The Dawn, Daybreak", verse 3)
Ibn ‘Abbaas said: "The even is the Day of al-Adhaa [i.e., 10th Dhoo'l-Hijjah] and the odd is
the Day of Arafat [i.e., 9th Dhoo'l-Hijjah] This is also the view of ‘Ikrimah and al-Dahhaak".
4. Fasting on this day is an expiation for two years.
It was reported from Abu Qutaadah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings of Allah be upon him) was asked about fasting on the Day of Arafat. He said, "It expiates for the sins of the
previous year and of the coming year." Narrated by Muslim.
This (fasting) is mustahabb for those who are not on Hajj. In the case of the one who is on Hajj, it is not Sunnah for him to fast on the Day of Arafat, because the Prophet (peace and blessings of Allah be upon him) did not fast
on this day in Arafat. It was narrated that he forbade fasting on the Day of Arafat in Arafat.
5. It is the day on which Allah took the covenant from the progeny of Adam.
It was reported that Ibn ‘Abbaas (may Allah be pleased with him) said: The Messenger of Allah (peace and blessings of Allah be upon him) said:
"Allah took the covenant from the loins of Adam in Na'maan, i.e., Arafat.
He brought forth from his loins all his offspring and spread them before Him, then He addressed them, and said: ‘Am I not your Lord? They said,
‘Yes, we testify,' let you should say on the Day of Resurrection: ‘Verily, we have been unaware of this.' Or lest you should say: ‘It was only our fathers aforetime who took others as partners in worship along with Allah, and we were (merely their) descendants after them; will You then destroy us because of the deeds of men who practiced Al-Baatil (i.e., polytheism and
committing crimes and sins, invoking and worshipping others besides Allah)?'" [The Holy Quran, Surah 7. "The Heights", verses 172-173]
(Narrated by Ahmad and classed as saheeh by al-Albaani.
And there is no greater day than this and no greater covenant than this).
6. It is the day of forgiveness of sins, freedom from the Fire and pride in the people who are there:
In Saheeh Muslim it was narrated from ‘Aa'ishah (may Allah be pleased with her) that the Prophet (peace and blessings of Allah be upon him) said:
"There is no day on which Allah frees more people from the Fire than the Day of Arafat. He comes close and expresses His pride to the angels, saying, ‘What do these people want?'"
It was reported from Ibn ‘Umar that the Prophet (peace and blessings of Allah be upon him) said:
"Allah expresses His pride to His angels at the time of ‘Ishaa' on the Day of Arafat, about the people of Arafat. He says, ‘Look at My slaves who have come unkempt and dusty.'"
(Narrated by Ahmad and classed as saheeh by al-Albaani).
And Allah knows best.

God bless for this contribution.