Sunan an-Nasa'i, Volume 5, Book 45, Hadith 4752 (DarusSalam) ⓘ
It was narrated that Abu Bakrah said: The Messenger of Allah said: "Whoever kills a Mu'ahad with no justification, Allah will forbid Paradise to him and he will not even smell its fragrance."
أَخْبَرَنَا الْحُسَيْنُ بْنُ حُرَيْثٍ، قَالَ حَدَّثَنَا إِسْمَاعِيلُ، عَنْ يُونُسَ، عَنِ الْحَكَمِ بْنِ الأَعْرَجِ، عَنِ الأَشْعَثِ بْنِ ثُرْمُلَةَ، عَنْ أَبِي بَكْرَةَ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ قَتَلَ نَفْسًا مُعَاهِدَةً بِغَيْرِ حِلِّهَا حَرَّمَ اللَّهُ عَلَيْهِ الْجَنَّةَ أَنْ يَشُمَّ رِيحَهَا " .
also referenced under: Hadith 4748 (Reference) & Book 45, Hadith 43 (In-Book)