On the authority of Ibn Masood (may Allah be pleased with him) who said:
The Messenger of Allah (peace and blessings of Allah be upon him) said, “It is not permissible to spill the blood of a Muslim except in three [instances]: the married person who commits adultery, a life for a life, and the one who forsakes his religion and separates from the community.” [Al-Bukhari] [Muslim]
عَنْ ابْنِ مَسْعُودٍ رَضِيَ اللهُ عَنْهُ قَالَ: قَالَ رَسُولُ اللَّهِ صلى الله عليه و سلم "لَا يَحِلُّ دَمُ امْرِئٍ مُسْلِمٍ [ يشهد أن لا إله إلا الله، وأني رسول الله] إلَّا بِإِحْدَى ثَلَاثٍ: الثَّيِّبُ الزَّانِي، وَالنَّفْسُ بِالنَّفْسِ، وَالتَّارِكُ لِدِينِهِ الْمُفَارِقُ لِلْجَمَاعَةِ".
[رَوَاهُ الْبُخَارِيُّ]
، [وَمُسْلِمٌ]