Sunan an-Nasa'i, Volume 5, Book 37, Hadith 4064 (DarusSalam) ⓘ
Ibn 'Abbas said: "The Messenger of Allah [SAW] said: 'Whoever changes his religion, kill him.'"
أَخْبَرَنَا عِمْرَانُ بْنُ مُوسَى، قَالَ حَدَّثَنَا عَبْدُ الْوَارِثِ، قَالَ حَدَّثَنَا أَيُّوبُ، عَنْ عِكْرِمَةَ، قَالَ قَالَ ابْنُ عَبَّاسٍ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ بَدَّلَ دِينَهُ فَاقْتُلُوهُ " .
also referenced under: Hadith 4059 (Reference) & Book 37, Hadith 94 (In-Book)