il bue che dice cornuto all'asino

Italian

Etymology

Literally “the ox calling the donkey horned” (cornuto also meaning “cuckold”)

Phrase

1. (idiomatic) pot calling the kettle black (somebody who accuses someone else of a fault shared by the accuser)
2. (idiomatic) it takes one to know one
3. (idiomatic) I know you are but what am I