Hadith 4056
أَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ، قَالَ حَدَّثَنَا شَرِيكٌ، عَنْ أَبِي إِسْحَاقَ، عَنْ عَامِرٍ، عَنْ جَرِيرٍ، قَالَ أَيُّمَا عَبْدٍ أَبَقَ مِنْ مَوَالِيهِ وَلَحِقَ بِالْعَدُوِّ فَقَدْ أَحَلَّ بِنَفْسِهِ .
It was narrated that Jarir said:
"Any slave who runs away from his masters and joins the enemy, he has made it permissible to shed his blood."
Reference : Sunan an-Nasa'i 4056
In-book reference : Book 37, Hadith 91