It was narrated from Abu Hurairah that the Prophet (ﷺ) said:
“Whoever kills a Mu'ahid who has the protection of Allah and the protection of his Messenger, will not smell the fragrance of Paradise, even though its fragrance may be detected from a distance of Seventy years.”
حَدَّثَنَا مُحَمَّدُ بْنُ بَشَّارٍ، حَدَّثَنَا مَعْدِيُّ بْنُ سُلَيْمَانَ، أَنْبَأَنَا ابْنُ عَجْلاَنَ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏ "‏ مَنْ قَتَلَ مُعَاهِدًا لَهُ ذِمَّةُ اللَّهِ وَذِمَّةُ رَسُولِهِ لَمْ يَرَحْ رَائِحَةَ الْجَنَّةِ وَإِنَّ رِيحَهَا لَيُوجَدُ مِنْ مَسِيرَةِ سَبْعِينَ عَامًا ‏"‏ ‏.‏
GradeSahih (Darussalam)
English reference : Vol. 3, Book 21, Hadith 2687
Arabic reference : Book 21, Hadith 2789