וְהֵם֙ לֹ֣א יָֽדְע֔וּ כִּ֥י שֹׁמֵ֖עַ יוֹסֵ֑ף כִּ֥י הַמֵּלִ֖יץ בֵּינֹתָֽם׃
Targum Jonathan on Genesis
But they knew not that Joseph understood (heard) the holy language; for Menasheh was interpreter between them.
Targum Jerusalem
But they knew not that Joseph heard in the holy language; for as an interpeter Menasheh stood between them.