Arthashastra
सिद्ध प्रव्रजित चैत्य स्तूप दैवत प्रतिमानाम् अभीक्ष्ण अभिगमनेषु वा भूमि गृह सुरुङ्ग आरूढ भित्ति प्रविष्टास् तीक्ष्णाः परम् अभिहन्युः ॥
When the enemy is in the habit of paying frequent visits to ascetics, altars, sacred pillars (stúpa), and images of gods, spies hidden in underground chambers or in subterranean passages, or inside the walls, may strike him down.
english translation
siddha pravrajita caitya stUpa daivata pratimAnAm abhIkSNa abhigamaneSu vA bhUmi gRha suruGga ArUDha bhitti praviSTAs tIkSNAH param abhihanyuH ॥
hk transliteration by Sanscript