A Jewish man came to Umar and said, "Commander of the Believers, there is a verse in your Book that you recite. Had it been revealed to us, the community of Jews, we would have taken that day as a festival."Umar asked, "Which verse is that?"He replied, "This day I have perfected for you your religion and completed My favor upon you and have approved for you Islam as your religion" [Maidah 5:3].Umar said, "I know the day on which it was revealed and the place where it was revealed. It was revealed to the Messenger of Allah ﷺ at Arafat on a Friday."
جاء رجل من اليهود إلى عمر، فقال: يا أمير المؤمنين، آية في كتابكم تقرؤونها، لو علينا نزلت- معشر اليهود- لاتخذنا ذلك اليوم عيدا. فقال: واي آية؟ قال: {اليوم أكملت لكم دينكم وأتممت عليكم نعمتي ورضيت لكم الإسلم دينا} فقال عمر: إني لأعلم اليوم الذي نزلت فيه، والمكان الذي نزلت فيه، نزلت على رسول الله ﷺ بعرفات في يوم جمعة.
Bukhari narrated it in the Book of Faith (45), and Muslim narrated it in Tafsir (3017:5), both through the route of Jafar bin Awn, who said, Abu Umays narrated to us, who said, Qays bin Muslim informed us, from Tariq bin Shihab, who said, and then he mentioned it. The wording given here is Muslim's, and Bukhari's wording is similar.In a narration recorded by Bukhari (4606) through the route of Sufyan, from Qays, "the day of Arafah, and we were, by Allah, at Arafah." Sufyan said, "And I am not sure whether it was a Friday or not, "This day I have perfected your religion for you" [Maidah 5:3]."This is how the doubt arose from Sufyan regarding specifying the day. The mass-transmitted reports confirm that it was indeed a Friday, so Sufyan's doubt should be understood as meaning that he could not recall whether his teacher had named the day or not, and so he refrained from stating with certainty that it was Friday.