ENOfficial
It was narrated from 'Amr bin Shu'aib, from his father, from his grandfather, that the Messenger of Allah (ﷺ) said: “A Muslim should not be killed in retaliation for the murder of a disbeliever.”
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا هِشَامُ بْنُ عَمَّارٍ، حَدَّثَنَا حَاتِمُ بْنُ إِسْمَاعِيلَ، حَدَّثَنَا عَبْدُ الرَّحْمَنِ بْنُ عَيَّاشٍ، عَنْ عَمْرِو بْنِ شُعَيْبٍ، عَنْ أَبِيهِ، عَنْ جَدِّهِ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " لاَ يُقْتَلُ مُسْلِمٌ بِكَافِرٍ " .
sunnah.com