pot call the kettle black
pot call the kettle black {informal}
The person who is criticizing someone else is as guilty as the person he accuses; the charge is as true of the person who makes it as of the one he makes it against.
When the commissioner accused the road builder of bribery, the contractor said the pot was calling the kettle black.
Bill said John was cheating at a game but John replied that the pot was calling the kettle black.
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Source: A Dictionary of American Idioms