The pot calling the kettle black
The notion that a criticism that a person makes of another could equally well apply to themself.
This phrase originates in Cervantes' Don Quixote, or at least in Thomas Shelton's 1620 translation - Cervantes Saavedra's History of Don Quixote:
"You are like what is said that the frying-pan said to the kettle, 'Avant, black-browes'."
The first person who is recorded as using the phrase in English was William Penn, the founder of Pennsylvania, in his Some fruits of solitude, 1693:
"For a Covetous Man to inveigh against Prodigality... is for the Pot to call the Kettle black."
Shakespeare had previously expressed a similar notion in a line in Troilus and Cressida, 1606:
"The raven chides blackness."