كتاب الحدود
Read the English translation first, with the original Arabic directly underneath.
Jarir reported the prophet (ﷺ) as saying:
When a slave runs away and reverts to polytheism, he may lawfully be killed.
إِذَا أَبَقَ الْعَبْدُ إِلَى الشِّرْكِ فَقَدْ حَلَّ دَمُهُ