Sahih al-Bukhari 45
Narrated 'Umar bin Al-Khattab:
Once a Jew said to me, "O the chief of believers! There is a verse in 
     your Holy Book Which is read by all of you (Muslims), and had it been 
     revealed to us, we would have taken that day (on which it was revealed
     as a day of celebration." 'Umar bin Al-Khattab asked, "Which is that 
     verse?" The Jew replied, "This day I have perfected your religion For 
     you, completed My favor upon you, And have chosen for you Islam as 
     your religion." (5:3) 'Umar replied,"No doubt, we know when and where 
     this verse was revealed to the Prophet. It was Friday and the Prophet (ﷺ) 
     was standing at 'Arafat (i.e. the Day of Hajj)"
حَدَّثَنَا الْحَسَنُ بْنُ الصَّبَّاحِ، سَمِعَ جَعْفَرَ بْنَ عَوْنٍ، حَدَّثَنَا أَبُو الْعُمَيْسِ، أَخْبَرَنَا قَيْسُ بْنُ مُسْلِمٍ، عَنْ طَارِقِ بْنِ شِهَابٍ، عَنْ عُمَرَ بْنِ الْخَطَّابِ، أَنَّ رَجُلاً، مِنَ الْيَهُودِ قَالَ لَهُ يَا أَمِيرَ الْمُؤْمِنِينَ، آيَةٌ فِي كِتَابِكُمْ تَقْرَءُونَهَا لَوْ عَلَيْنَا مَعْشَرَ الْيَهُودِ نَزَلَتْ لاَتَّخَذْنَا ذَلِكَ الْيَوْمَ عِيدًا‏.‏ قَالَ أَىُّ آيَةٍ قَالَ ‏{‏الْيَوْمَ أَكْمَلْتُ لَكُمْ دِينَكُمْ وَأَتْمَمْتُ عَلَيْكُمْ نِعْمَتِي وَرَضِيتُ لَكُمُ الإِسْلاَمَ دِينًا‏}‏‏.‏ قَالَ عُمَرُ قَدْ عَرَفْنَا ذَلِكَ الْيَوْمَ وَالْمَكَانَ الَّذِي نَزَلَتْ فِيهِ عَلَى النَّبِيِّ صلى الله عليه وسلم وَهُوَ قَائِمٌ بِعَرَفَةَ يَوْمَ جُمُعَةٍ‏.‏