The Messenger of Allah ﷺ said, "The blood of a Muslim who testifies that there is no god but Allah and that I am the Messenger of Allah is not lawful to shed except in three cases: a life for a life, the married person who commits adultery, and the one who abandons his religion and separates from the community."
قال رسول الله ﷺ: لا يحل دم امرئ مسلم يشهد أن لا إله إلا الله، وأني رسول الله إلا بإحدى ثلاث: النفس بالنفس، والثيب الزاني، والتارك لدينه المفارق للجماعة.
Bukhari narrated it in the Book of Blood Money (6878) and Muslim in the Book of Qasamah (1676), both through the route of Amash, from Abdullah bin Mura, from Masruq, from Abdullah bin Masud, who mentioned it.