'A’ishah (RAA) narrated that Allah’s Messenger (ﷺ) said:

“The blood of a Muslim is not to be shed except for three reasons: a married man who committed adultery, a man who kills another Muslim intentionally for which he must be killed (in Qisas or retaliation), and a man who abandons Islam and fights against Allah and His Messenger, in which case he should be either killed, crucified, or exiled.” Related by Abu Dawud and An-Nasa’i. Al-Hakim graded it as Sahih.

وَعَنْ عَائِشَةَ رَضِيَ اَللَّهُ عَنْهَا, عَنْ رَسُولِ اَللَّهِ ‏- صلى الله عليه وسلم ‏-قَالَ: { لَا يَحِلُّ قَتْلُ مُسْلِمٍ إِلَّا فِي إِحْدَى ثَلَاثِ خِصَالٍ: زَانٍ مُحْصَنٌ فَيُرْجَمُ, وَرَجُلٌ يَقْتُلُ مُسْلِمًا مُتَعَمِّدًا فَيُقْتَلُ, وَرَجُلٌ يَخْرُجُ مِنْ اَلْإِسْلَامِ فَيُحَارِبُ اَللَّهَ وَرَسُولَهُ, فَيُقْتَلُ, أَوْ يُصْلَبُ, أَوْ يُنْفَى مِنْ اَلْأَرْضِ .‏ } رَوَاهُ أَبُو دَاوُدَ, وَالنَّسَائِيُّ, وَصَحَّحَهُ اَلْحَاكِمُ [1]‏ .‏