Bulugh al-Maram, Book 9, Hadith 1242 (English) ⓘ
Ibn 'Abbas (RAA) narrated that The Messenger of Allah said, “He who changes his religion (i.e. apostates) kill him.” Related by Al-Bukhari.
وَعَنْ اِبْنِ عَبَّاسٍ رَضِيَ اَللَّهُ عَنْهُمَا قَالَ: قَالَ رَسُولُ اَللَّهِ - صلى الله عليه وسلم -{ مَنْ بَدَّلَ دِينَهُ فَاقْتُلُوهُ } رَوَاهُ اَلْبُخَارِيُّ
also referenced under: Book 9, Hadith 1214 (In-Book)