Manusmriti

siva.sh/manusmriti/7/105

नास्य छिद्रं परो विद्याद् विद्यात्छिद्रं परस्य च । गूहेत् कूर्म इवाङ्गानि रक्षेद् विवरमात्मनः ॥ १०५ ॥

sanskrit

His enemy must not know his weaknesses, but he must know the weaknesses of his enemy; as the tortoise (hides its limbs), even so let him secure the members (of his government against treachery), let him protect his own weak points.

english translation

nAsya chidraM paro vidyAd vidyAtchidraM parasya ca | gUhet kUrma ivAGgAni rakSed vivaramAtmanaH || 105 ||

hk transliteration by Sanscript