Kautilya's Arthashastra 5.1.3

5.1.3

rājānam avagṛhyopajīvinaḥ śatrusādhāraṇā vā ye mukhyās teṣu gūḍhapuruṣapraṇidhiḥ kṛtyapakṣopagraho vā siddhiḥ yathoktaṃ purastād, upajāpo 'pasarpo vā yathā pāragrāmike vakṣyāmaḥ //

With regard to those chiefs who, though living by service under the king, are inimically disposed towards him, or have taken the side of his enemy, a spy with secret mission or one in the guise of an ascetic and devoted to the king's cause shall set to work as described before; or a spy trained in the art of sowing the seeds of dissension may set to work, as will be described in connection with the ‘Invasion of an enemy's villages.’