Sunan Ibn Majah, Book 20, Hadith 2632 (In-Book) ⓘ
It was narrated from Ibn`Abbas that the Messenger of Allah said: “Whoever changes his religion, execute him.”
حَدَّثَنَا مُحَمَّدُ بْنُ الصَّبَّاحِ، أَنْبَأَنَا سُفْيَانُ بْنُ عُيَيْنَةَ، عَنْ أَيُّوبَ، عَنْ عِكْرِمَةَ، عَنِ ابْنِ عَبَّاسٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم (مَنْ بَدَّلَ دِينَهُ فَاقْتُلُوهُ ).
also referenced under: Hadith 2535 (Reference) & Volume 3, Book 20, Hadith 2535 (DarusSalam)