Musnad Ahmad 2:107

Ja'far ibn 'Awn narrated to us, Abu 'Umays narrated to us, from Qays ibn Muslim, from Tariq ibn Shihab, who said: A man from the Jews came to 'Umar and said: "O Commander of the Faithful, you recite a verse in your Book; if it had been revealed to us, the company of Jews, we would have taken that day as an Eid (festival)." 'Umar said: "And which verse is it?" He said: "The saying of the Almighty, the Majestic: 'This day I have perfected for you your religion and completed My favor upon you' [Al-Ma'idah: 3]." 'Umar said: "By Allah, I indeed know the day it was revealed to the Messenger of Allah, may Allah bless him and grant him peace, and the hour in which it was revealed to the Messenger of Allah, may Allah bless him and grant him peace: the evening of 'Arafah on a Friday."