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 ‏"‏ ‏.‏

It was narrated from Ibn 'Abbas that the Prophet (PBUH) 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.” Translation Not Available

Book Ref: Sunan Ibn Majah Book 21 Hadith 2660
Web Ref:  Sunan Ibn Majah Vol 3 Book 21 Hadith 2660