When it is permissible to shed the blood of a muslim
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا حَفْصُ بْنُ غِيَاثٍ، وَأَبُو مُعَاوِيَةَ وَوَكِيعٌ عَنِ الأَعْمَشِ، عَنْ عَبْدِ اللَّهِ بْنِ مُرَّةَ، عَنْ مَسْرُوقٍ، عَنْ عَبْدِ اللَّهِ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " لاَ يَحِلُّ دَمُ امْرِئٍ مُسْلِمٍ يَشْهَدُ أَنْ لاَ إِلَهَ إِلاَّ اللَّهُ وَأَنِّي رَسُولُ اللَّهِ إِلاَّ بِإِحْدَى ثَلاَثٍ الثَّيِّبُ الزَّانِ وَالنَّفْسُ بِالنَّفْسِ وَالتَّارِكُ لِدِينِهِ الْمُفَارِقُ لِلْجَمَاعَةِ " .
'Abdullah (b. Mas'ud) reported Allah's Messenger (ﷺ) as saying: It is not permissible to take the life of a Muslim who bears testimony (to the fact that there is no god but Allah, and I am the Messenger of Allah, but in one of the three cases: the married adulterer, a life for life, and the deserter of his Din (Islam), abandoning the community.