Tafsir of Yusuf 12:74

(They said): meaning the companions of Yusuf, peace be upon him.

(What is its retribution?): meaning the [stolen] measuring bowl. The discourse involves the ellipsis of an attributed noun, meaning: "What is the retribution for its theft?" The pronoun refers to either the theft or the thief. Retribution is ascribed to the offense in reality, and to the one who committed it metaphorically. It may also be said that there is an ellipsis of an attributed noun; so understand this. The intended meaning is: "What is the retribution for that according to you and in your law?"

(If you are liars): meaning, in claiming innocence, as is the apparent sense. The use of the conditional particle 'in' (if) serves to show consideration for their position.