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." (Using translation from Nasāʾī 4748)
قَالَ رَسُولُ اللهِ ﷺ مَنْ قَتَلَ نَفْسًا مُعَاهَدَةً بِغَيْرِ حِلِّهَا حَرَّمَ اللهُ عَلَيْهِ الْجَنَّةَ أَنْ يَشُمَّ رِيحَهَا