Thirukkural 587

மறைந்தவை கேட்கவற் றாகி அறிந்தவை ஐயப்பாடு இல்லதே ஒற்று.

Maraindhavai ketkavattrAki arindhavai Aiyappaadu illathE otru.

What is hidden becomes known through inquiry; what is known admits no doubt—such is the mark of the spy. / The true spy rests in certainty about what is hidden and questions nothing about what is revealed.