Exodus 7:1
וַיֹּאמֶר ה' אֶל מֹשֶׁה רְאֵה נְתַתִּיךָ אֱלֹהִים לְפַרְעֹה וְאַהֲרֹן אָחִיךָ יִהְיֶה נְבִיאֶ
Hashem said to Moses, "Behold, I have set you you as a judge over Pharaoh and your brother Aaron will be your prophet."
The word "elohim" used to describe Moshe in this verse means a judge or a person of might, but it can also mean a god (or even G-d Himself). The word "navi" used to describe Aharon means a spokesman, but it later came to mean a prophet. Accordingly, Onkelos clarifies this verse by translating it as "I have appointed you teacher to Pharaoh and your brother Aharon will be your interpreter."