It was narrated from Ibn 'Abbas that the Prophet (ﷺ) said:”A believer should not be killed in retaliation for the murder of a disbeliever, and a person who has a treaty should not be killed during the time of the treaty.”
حَدَّثَنَا مُحَمَّدُ بْنُ عَبْدِ الأَعْلَى الصَّنْعَانِيُّ، حَدَّثَنَا مُعْتَمِرُ بْنُ سُلَيْمَانَ، عَنْ أَبِيهِ، عَنْ حَنَشٍ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " لاَ يُقْتَلُ مُؤْمِنٌ بِكَافِرٍ وَلاَ ذُو عَهْدٍ فِي عَهْدِهِ " .
IbnMaja
The Chapters on Blood Money • Hadith 2660