pot calling the kettle black, the - Phrases/Idioms
The American Heritage® Dictionary of Idioms by Christine Ammer. Copyright © 2003, 1997 by The Christine Ammer 1992 Trust. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
Accusing someone of faults that one has oneself, as in Tom's criticizing Dexter for dubious line calls is a case of the pot calling the kettle black, since Tom's about the worst line judge I've ever seen. This expression dates from the days of open-hearth cooking, which blackens practically all the utensils used. [Early 1600s]