(14) باب الْحُكْمِ فِي الْمُرْتَدِّ
It was narrated from Ibn 'Umar that:
'Uthman said: "I heard the Messenger of Allah [SAW] say: 'It is not permissible to shed the blood of a Muslim except in three cases: A man who commits adultery after having married; or one who kills intentionally, in which case he deserves retaliation; or one who apostatizes after having become Muslim, in which case he deserves to be killed.'"
Reference: Sunan an-Nasa'i 4057
In-book reference: Book 37, Hadith 92
English translation: Vol. 5, Book 37, Hadith 4062