Sayyiduna Anas (may Allah be pleased with him) narrated that the Prophet (peace and blessings be upon him) sent an expedition in which the participants were called the Qurra (i.e., reciters of the Qur'an). All of them were martyred. I have never seen the Prophet (peace and blessings be upon him) grieve over anything as much as he grieved over their martyrdom. Consequently, the Messenger of Allah (peace and blessings be upon him) supplicated against their killers in the Fajr prayer for a month. He would say: "‘Usayyah has disobeyed Allah and His Messenger."
Hadith Referenceاللؤلؤ والمرجان / كتاب المساجد ومواضع الصلاة / 395
Hadith Gradingمحدثین:«صحیح»
Hadith Takhrij«صحیح، أخرجه البخاري في: 8 كتاب الدعوات: 58 باب الدعاء على المشركين»