أَخْبَرَنَا إِسْمَاعِيلُ بْنُ مَسْعُودٍ، قَالَ حَدَّثَنَا خَالِدٌ، عَنْ عُيَيْنَةَ، قَالَ أَخْبَرَنِي أَبِي قَالَ، قَالَ أَبُو بَكْرَةَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ مَنْ قَتَلَ مُعَاهِدًا فِي غَيْرِ كُنْهِهِ حَرَّمَ اللَّهُ عَلَيْهِ الْجَنَّةَ ‏"‏ ‏.‏
Translation
It was narrated that 'Abdullah bin 'Amr said

"The Messenger of Allah said: 'Whoever kills a person from among Ahl Adh-Dhimmah, he will not smell the fragrance of Paradise, and its fragrance may be detected from a distance of forty years."