Full Sharh — Mishkat al-Masabih 3316
وَعَنْ عَبْدِ اللَّهِ بْنِ عَمْرٍو رَضِيَ اللَّهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «مَنْ قَتَلَ مُعَاهِدًا لَمْ يَرَحْ رَائِحَةَ الْجَنَّةِ وَإِنَّ رِيحَهَا تُوجَدُ مِنْ مَسِيرَةِ أربعينَ خَرِيفًا» . رَوَاهُ البُخَارِيّ
English Translation
‘Abdallah b. ‘Amr reported God’s Messenger as saying, “If anyone kills a man who has made a covenant* he will not experience the fragrance of paradise, yet its odour can be experienced at a distance of forty years’ journey.” Bukhari transmitted it. * Mu'ahid. This is used of a member of protected communities, but is also used of anyone who belongs to a non-Muslim community with whom a treaty of peace has been made.
Source
Mishkat al-Masabih(مشكاة المصابيح)
Retaliation
Hadith Number
3316