The Day of Arafat is on the day before Eid Al-Adha.
https://en.m.wikipedia.org/wiki/Day_of_Arafah
Abu Qatada al-Ansari narrated that Muhammad was asked about fasting on the day of Arafah, whereupon he said:
It expiates the sins of the preceding year and the coming year. Also about fasting on the Ashura(10 Muharram) he said: It expiates the sins of the preceding year.
In Sahih Muslim it was narrated from Aisha that Muhammad said:
'There is no day on which Allah frees more people from the Fire than the Day of Arafah. He comes close and expresses His fulfillment to the angels, saying, 'What do these people want?'
Sura 5 - Al Ma'idah - The Banquet Table
Verse 3
The following are from the footnotes of The Meaning of the Holy Qur'an in Today's English by Sheikh Yahiya Emerick.
On the quoted [5:3]:
This was one of the last passages revealed to Prophet Muhammad, indicating that his ministry was coming at an end. The name of the religion, Islam, or surrender to God’s will, is given in this verse. It was revealed on a Friday during the Prophet’s Farewell Pilgrimage in the year 632 and recited to the gathered throng of 100,000 people on what is known as the Day of Arafat. While many Muslims were elated at this confident statement from God, ‘Umar ibn al-Khattab began to weep openly. When the Prophet asked him why he was weeping, ‘Umar replied, “This verse seems to signal that your time in this world is drawing to a close. With the perfection of Islam, the need for a messenger has been fulfilled.” The Prophet replied in the affirmative. Eighty days later, the Prophet passed away, leaving ‘Umar distraught and despondent. Some years later, after ‘Umar had been elevated to the office of caliph, a Jewish man in Medina approached ‘Umar and said, “Leader of the Muslims, you recite a verse in your book that, if it were revealed to us, would have caused us to make that day a holiday.” Umar replied, “Which verse is that?” Then the Jew read this verse. ‘Umar exclaimed, “I swear to God that I know the day in which it was revealed to the Messenger and its hour. It was late in the daytime on the day of ‘Arafat on a Friday.” (Bukhari, Muslim)
On [62:11]:
The Prophet said, “The promised day is the Day of Resurrection. The witnessed day is the Day of Arafat, and the witness is Friday. The sun has neither risen nor set on a day better than it. There is a time (on Friday) in which a faithful servant who is praying to God for good will find God responding to him. If he seeks to be protected from something, God will keep him safe from it.” (Ahmad, Tirmidhi)
