"It is not permissible to kill a Muslim except in one of three cases: A adulterer who has been married, who is to be stoned; a man who kills a Muslim deliberately; and a man who leaves Islam and wages war against Allah, the Mighty and Sublime, and His Messenger, who is to be killed, crucified or banished from the land."
عَنْ رَسُولِ اللَّهِ ﷺ أَنَّهُ قَالَ لاَ يَحِلُّ قَتْلُ مُسْلِمٍ إِلاَّ فِي إِحْدَى ثَلاَثِ خِصَالٍ زَانٍ مُحْصَنٍ فَيُرْجَمُ وَرَجُلٌ يَقْتُلُ مُسْلِمًا مُتَعَمِّدًا وَرَجُلٌ يَخْرُجُ مِنَ الإِسْلاَمِ فَيُحَارِبُ اللَّهَ ﷻ وَرَسُولَهُ فَيُقْتَلُ أَوْ يُصَلَّبُ أَوْ يُنْفَى مِنَ الأَرْضِ