Sahih al-Bukhari, Hadith 6878 ⓘ
Narrated `Abdullah: Allah's Messenger said, "The blood of a Muslim who confesses that none has the right to be worshipped but Allah and that I am His Apostle, cannot be shed except in three cases: In Qisas for murder, a married person who commits illegal sexual intercourse and the one who reverts from Islam (apostate) and leaves the Muslims."
حَدَّثَنَا عُمَرُ بْنُ حَفْصٍ، حَدَّثَنَا أَبِي، حَدَّثَنَا الأَعْمَشُ، 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 النَّفْسُ بِالنَّفْسِ وَالثَّيِّبُ الزَّانِي، وَالْمَارِقُ مِنَ الدِّينِ التَّارِكُ الْجَمَاعَةَ " .
also referenced under: Book 87, Hadith 17 (In-Book) & Volume 9, Book 83, Hadith 17 (USC-MSA)