Arthashastra
स चेद् दण्डं दद्यान् न स्वयम् आगच्छेत् तम् अस्य वैरिणा घातयेत् ॥
If the enemy refuses to meet any man in person, then also attempts may be made to kill him by employing his enemy.
english translation
sa ced daNDaM dadyAn na svayam Agacchet tam asya vairiNA ghAtayet ॥
hk transliteration by Sanscript