Bereshit 42:23

והם לא ידעו כי שמע יוסף AND THEY KNEW NOT THAT JOSEPH שמע UNDERSTOOD their language, and they said this in his presence. כי המליץ בינתם FOR THE INTERPRETER WAS BETWEEN THEM — for when they had spoken to him there was an interpreter between them who knew both the Hebrew and the Egyptian languages. He interpreted their words to Joseph and Joseph’s words to them. Consequently they were under the impression that Joseph did not understand the Hebrew language. המליץ THE INTERPRETER — This was Manasseh (Genesis Rabbah 91:8).

וְהֵם֙ לֹ֣א יָֽדְע֔וּ כִּ֥י שֹׁמֵ֖עַ יוֹסֵ֑ף כִּ֥י הַמֵּלִ֖יץ בֵּינֹתָֽם׃

And they knew not that Yosef understood them; for he spoke to them by an interpreter.