The Prophet ﷺ said: If anyone kills a man whom he grants protection prematurely, Allah will forbid him to enter Paradise. (Using translation from Abū Dāʾūd 2760)
قَالَ رَسُولُ اللهِ ﷺ مَنْ قَتَلَ مُعَاهَدًا فِي غَيْرِ كُنْهِهِ حَرَّمَ اللهُ عَلَيْهِ الْجَنَّةَ أَنْ يَجِدَ رِيحَهَا