Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) said that a man said to Umar (may Allah be pleased with him): O Commander of the Believers! There is a verse in your Book which you recite; had it been revealed to us Jews, we would have celebrated that day as a festival (Eid). He (may Allah be pleased with him) asked: Which verse is it? He said: "This day I have perfected your religion for you, completed My favour upon you, and chosen Islam as your religion." [Surah al-Ma'idah: 3] So Umar (may Allah be pleased with him) said: We know that day, and also the place where this verse was revealed to the Prophet (peace and blessings be upon him); this verse was revealed to him (peace and blessings be upon him) on the plain of Arafat on a Friday.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9478
Tariq bin Shihab said that a Jew said to Umar bin al-Khattab (may Allah be pleased with him): If only this verse, "This day I have perfected your religion for you" (to the end of the verse) [Surah al-Ma'idah: 3], had been revealed to us Jews, we would have celebrated that day as a festival (Eid). So Umar (may Allah be pleased with him) said: I know the place, the day and the time when this verse was revealed. It was revealed to the Messenger of Allah (peace and blessings be upon him) while we were at Arafah, on the afternoon of Friday.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9479
Sayyidah Aishah (may Allah be pleased with her) said that the Prophet (peace and blessings be upon him) said: "There is no day on which Allah Almighty frees more servants from Hell than the day of Arafah. He draws near and boasts of them before the angels, saying: What have these people come for?"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9480
Sayyiduna Abbas bin Mirdas (may Allah be pleased with him) said that the Prophet (peace and blessings be upon him) supplicated on the night of Arafah for forgiveness and mercy for his Ummah, and supplicated abundantly. Allah Almighty revealed to him (peace and blessings be upon him): "I have done this: the sins that are between Me and them I have forgiven, but their wrongdoing is not forgiven." He (peace and blessings be upon him) said: "O Allah! You are able to give this wronged person a reward better than (what he suffered from) the wrong done to him, and to forgive this wrongdoer." But this supplication was not answered that night. When it was the morning of Muzdalifah, he (peace and blessings be upon him) repeated this supplication, and Allah Almighty, accepting it, said: "I have forgiven them." Then the Prophet (peace and blessings be upon him) smiled, and his Companions (may Allah be pleased with them) asked: "You (peace and blessings be upon him) have smiled at a time when you did not smile before?" He (peace and blessings be upon him) said: "I am smiling at the enemy of Allah, Iblis: when he learned that my supplication concerning my Ummah had been accepted, he began to cry out for ruin and destruction and to throw dust upon his head."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 9481