The Book of Oaths, Muharibin, Qasas (Retaliation), and Diyat (Blood Money)
Ṣaḥīḥ Muslim 4375
لاَ إِلَهَ إِلاَّ اللَّهُ وَأَنِّي رَسُولُ اللَّهِ إِلاَّ بِإِحْدَى ثَلاَثٍ الثَّيِّبُ الزَّانِ وَالنَّفْسُ بِالنَّفْسِ وَالتَّارِكُ لِدِينِهِ الْمُفَارِقُ لِلْجَمَاعَةِ
lā ilaha illā-Llāh wa-annī rasūlu-Llāh illā biʾiḥdā thalāthin ath-thayyibu az-zāni wa-an-nafsu bi-an-nafsi wa-at-tāriku lidīnihi al-mufāriqu liljamāʿah
Transliteration generated from the Arabic vowel marks
The full narration
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
Source
Ṣaḥīḥ Muslim · 4375
- Agreed upon as authentic (al-Bukhārī / Muslim)