Thirukkural 588

ஒற்றொற்றித் தந்த பொருளையும் மற்றுமோர் ஒற்றினால் ஒற்றிக் கொளல்.

Oṟṟoṟṟit tandha porullaiyum maṟṟumōr Oṟṟinaal oṟṟik kōḷal

Do not accept what another has earned through espionage, even if offered to you by yet another spy. Reject such knowledge entirely.