Sunan an-Nasa'i, Hadith 4065 ⓘ
It was narrated from Anas that : 'Ali came to some people of Az-Zutt, who worshipped idols, and burned them. Ibn 'Abbas said: "But the Messenger of Allah [SAW] said: 'Whoever changes his religion, kill him.'"
أَخْبَرَنَا مُحَمَّدُ بْنُ الْمُثَنَّى، قَالَ حَدَّثَنَا عَبْدُ الصَّمَدِ، قَالَ حَدَّثَنَا هِشَامٌ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، أَنَّ عَلِيًّا، أُتِيَ بِنَاسٍ مِنَ الزُّطِّ يَعْبُدُونَ وَثَنًا فَأَحْرَقَهُمْ، قَالَ ابْنُ عَبَّاسٍ إِنَّمَا قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ بَدَّلَ دِينَهُ فَاقْتُلُوهُ " .
also referenced under: Book 37, Hadith 100 (In-Book) & Volume 5, Book 37, Hadith 4070 (DarusSalam)