Mishkat al-Masabih 16 Retaliation كتاب القصاص 94

وَعَنْ أَبِي هُرَيْرَةَ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «الْإِيمَانُ قَيَّدَ الْفَتْكَ لَا يفتِكُ مُؤمنٌ» . رَوَاهُ أَبُو دَاوُد

Abu Huraira reported the Prophet as saying, “Faith is an assurance of safety from being killed unawares. A believer does not kill another unawares.” Abu Dawud transmitted it.