Sunan an-Nasa'i 4064
سنن النسائي#4064Sahihأَخْبَرَنَا 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
Scholarly Authentication
The label above is the grade most of these scholars gave — one dissenting opinion no longer speaks for all of them. If any scholar calls a narration fabricated, that verdict is shown instead, whatever the others say. Each scholar's own wording:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih
In-book reference: 37:99