it takes one to know one
This means that no one is better at finding a wrongdoer than another wrongdoer. So if you do something wrong, then you would know if someone else followed your mistake, or you would know someone with the same quality as yourself, did the same mistake if that makes any sense lmao. The example will help better your understanding.
it takes one to know one by GrammarQueen August 23, 2017
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