Sahih Bukhari
Sahih Bukhari Volume 002, Book 023, Hadith Number 387.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 23. Funerals (Al-Janaa'iz)
Narated By Anas : When the reciters of Quran were martyred, Allah's Apostle recited Qunut for one month and I never saw him (i.e. Allah's Apostle) so sad as he was on that day.