Arthashastra
तद् अवरुद्ध देशम् अतिनीय विश्वस्तं घातयेत् ॥
After leading him beyond that restricted territory, one should kill him once he has become trust ful.
english translation
tad avaruddha dezam atinIya vizvastaM ghAtayet ॥
hk transliteration by Sanscript