وَحَدَّثَنِي عَبْدُ بْنُ حُمَيْدٍ، أَخْبَرَنَا جَعْفَرُ بْنُ عَوْنٍ، أَخْبَرَنَا أَبُو عُمَيْسٍ، عَنْ قَيْسِ، بْنِ مُسْلِمٍ عَنْ طَارِقِ بْنِ شِهَابٍ، قَالَ جَاءَ رَجُلٌ مِنَ الْيَهُودِ إِلَى عُمَرَ فَقَالَ يَا أَمِيرَ الْمُؤْمِنِينَ آيَةٌ فِي كِتَابِكُمْ تَقْرَءُونَهَا لَوْ عَلَيْنَا نَزَلَتْ مَعْشَرَ الْيَهُودِ لاَتَّخَذْنَا ذَلِكَ الْيَوْمَ عِيدًا ‏.‏ قَالَ وَأَىُّ آيَةٍ قَالَ ‏{‏ الْيَوْمَ أَكْمَلْتُ لَكُمْ دِينَكُمْ وَأَتْمَمْتُ عَلَيْكُمْ نِعْمَتِي وَرَضِيتُ لَكُمُ الإِسْلاَمَ دِينًا‏}‏ فَقَالَ عُمَرُ إِنِّي لأَعْلَمُ الْيَوْمَ الَّذِي نَزَلَتْ فِيهِ وَالْمَكَانَ الَّذِي نَزَلَتْ فِيهِ نَزَلَتْ عَلَى رَسُولِ اللَّهِ صلى الله عليه وسلم بِعَرَفَاتٍ فِي يَوْمِ جُمُعَةٍ ‏.‏

Tariq b. Shihab reported that a Jew came to 'Umar and said: Commander of the Faithful, there is a verse in your Book, which you recite. Had it been revealed in connection with the Jews, we would have taken it as the day of rejoicing. Thereupon he said: Which verse do you mean? He replied:" This day I have perfected your religion for you and I have completed My favours upon you and I have chosen al-Islam as religion for you." Umar said, I know the day when it was revealed and the place where it was revealed. It was revealed to Allah's Messenger (PBUH) at 'Arafat on Friday. Translation Not Available

Book reference: Sahih Muslim Book 56 Hadith 7155
Web reference: Sahih Muslim Book 43 Hadith 3017 c