Sunan an Nasai 4063
The Book of Fighting [The Prohibition of Bloodshed]
أَخْبَرَنَا مُوسَى بْنُ عَبْدِ الرَّحْمَنِ، قَالَ حَدَّثَنَا مُحَمَّدُ بْنُ بِشْرٍ، قَالَ حَدَّثَنَا سَعِيدٌ، عَنْ قَتَادَةَ، عَنِ الْحَسَنِ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " مَنْ بَدَّلَ دِينَهُ فَاقْتُلُوهُ " . قَالَ أَبُو عَبْدِ الرَّحْمَنِ وَهَذَا أَوْلَى بِالصَّوَابِ مِنْ حَدِيثِ عَبَّادٍ .
It was narrated that Al-Hasan said:"The Messenger of Allah [SAW] said: 'Whoever changes his religion, kill him
Grading: Abu Ghuddah: Sahih Lighairihi · Al-Albani: Sahih · Zubair Ali Zai: Hasan
Text from the public-domain hadith-api dataset. Numbering follows that dataset and can differ by a few from some printed editions — check the wording, not only the number.