The Book of Fighting [The Prohibition of Bloodshed]
37/14. Chapter:
The Ruling on Apostates
Sunan an-Nasai
أَخْبَرَنَا الْحُسَيْنُ بْنُ عِيسَى، عَنْ عَبْدِ الصَّمَدِ، قَالَ حَدَّثَنَا هِشَامٌ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، أَنَّ ابْنَ عَبَّاسٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ بَدَّلَ دِينَهُ فَاقْتُلُوهُ " .
It was narrated from Anas that : Ibn 'Abbas said: "The Messenger of Allah [SAW] said: 'Whoever changes his religion, kill him.'"
Reference : Sunan an-Nasa'i 4064In-book reference : Book 37, Hadith 99English translation : Vol. 5, Book 37, Hadith 4069