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general::
Phrase(s): Set a thief to catch a thief.
Prov. The best person to catch a thief is another thief, because he or she knows how thieves think. • The government set a thief to catch a thief, hiring a stockbroker convicted of fraudulent practices to entrap the stockbroker they were investigating for fraud.
McGrawhill's American Idioms And Phrasal Verbs