You are the pot calling the kettle black when you point to another person and accuse that person of doing something that you are guilty of doing yourself. Example: "You are accusing me of being lazy? Ha! That's the pot calling the kettle black!"

"The pot" (for cooking) and "the kettle" (for boiling water) sit on the stove over the fire and become black from the flames. Example: "I'm tired of you always wearing my clothing!" Answer: "Aren't you the pot calling the kettle black? You're wearing my pants right now!"

The pot and the kettle are like old friends who have turned black with time; the pot only sees the blackness which is on the kettle; he doesn't see the black on himself. Example: "Here comes the guy who is always late for work." Answer: "Aren't you the pot calling the kettle black? You are usually the last person to show up!"