どの口くちが言いう

expression, godan verb (-u)

look who's talking; you're one to talk

Used to retort when someone criticizes or gives advice despite having the same fault or being in no position to do so. Often carries a sarcastic or indignant tone.

• 「遅ち刻こくするな」って、どの口くちが言いうの？

  You're telling me not to be late? Look who's talking!

• いつもサボってるくせに、どの口くちが言いうんだ。

  You're always slacking off, so you're one to talk.