Rashi on Genesis 42:23/רש"י על בראשית מ״ב:כ״ג

1והם לא ידעו כי שמע יוסף AND THEY KNEW NOT THAT JOSEPH שמע UNDERSTOOD their language, and they said this in his presence.

2כי 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.

3המליץ THE INTERPRETER — This was Manasseh (Genesis Rabbah 91:8).