Arthashastra
मित्र आसार मुख्य व्यञ्जनो वा सम्रुद्धेन मैत्रीं कृत्वा दूतम् अभित्यक्तं प्रेषयेत् "इदं ते छिद्रम्, इमे दूष्याः" "सम्रोद्धुर् वा छिद्रम्, अयं ते कृत्य पक्षः" इति ॥
A king pretending to be the enemy's chief friend or ally, may make the friendship closer with the besieged, and send a messenger to say: "This is thy weak point; these are thy internal enemies; that is the weak point of the besieger; and this person (who, deserting the conqueror, is now coming to thee) is thy partisan."
english translation
mitra AsAra mukhya vyaJjano vA samruddhena maitrIM kRtvA dUtam abhityaktaM preSayet "idaM te chidram, ime dUSyAH" "samroddhur vA chidram, ayaM te kRtya pakSaH" iti ॥
hk transliteration by Sanscript