Sahih Bukhari | Volume 6 | Hadith Number 130

Narrated by Tariq bin Shihab
The Jews said to 'Umar, "You (i.e. Muslims) recite a Verse, and had it been revealed to us, we would have taken the day of its revelation as a day of celebration." 'Umar said, "I know very well when and where it was revealed, and where Allah's Apostle was when it was revealed. (It was revealed on) the day of Arafat (Hajj Day), and by Allah, I was at Arafat" Sufyan, a sub-narrator said: I am in doubt whether the Verse: "This day I have perfected your religion for you." was revealed on a Friday or not.