Sahih Muslim 4377
صحيح مسلم#4377SahihAbdullah (b. Mas'ud) reported:Allah's Messenger (ﷺ) stood up and said: By Him besides Whom there is no god but He, the blood of a Muslim who bears the testimony that there is no god but Allah, and I am His Messenger, may be lawfully shed only in case of three persons: the one who abandons Islam, and deserts the community [Ahmad, one of the narrators, is doubtful whether the Prophet (ﷺ) used the word li'l-jama'ah or al-jama'ah), and the married adulterer, and life for life
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Every narration in Sahih Muslim is accepted as Sahih (authentic) by the established status of the book.
In-book reference: 28:36