hark who's talking
The person who just spoke is guilty of the same thing they have just criticized. A: "Kathy never pays attention in class." B: "Hark who's talking! Just today I saw you reading a magazine during the lecture."
hark who's talking
or look who's talking
People say Hark who's talking! or Look who's talking! to mean that something critical that someone has just said about someone else is true of them too. Hark who's talking! If you were so honest, we wouldn't be in this mess. `They're all mad.' `Look who's talking, you crazy old bat!'