This verse clarifies even more the plan explained in verse 15. He shall speak for you to the people means that Aaron is to speak in Moses’ behalf. The people probably refers primarily to the Israelites and the elders (see 3.13, 16) but does not exclude the Egyptians and even Pharaoh himself. Therefore one may express this first sentence as “He will speak for you to the people in Egypt.”

And he shall be a mouth for you is rendered as a metaphor in Revised Standard Version, and you shall be to him as God is a simile. The Hebrew uses the same construction for both clauses. To be a mouth for Moses is to be his “spokesman” (Good News Translation) or “mouthpiece” (New Jerusalem Bible). It may also be rendered as a simile along with the second clause, such as “he will be like your mouth, and you will be like his god” or “… like a god to him.” New International Version expresses both clauses in the same way: “and it will be as if he were your mouth and as if you were God to him.”

The purpose of all this is made clear in Good News Translation with the addition of “telling him what to say.” The word God need not be capitalized, since the relationship of Aaron to Moses is to be like that of a prophet to his god. Die Bibel im heutigen Deutsch makes this even clearer: “When Aaron speaks to the people for you, that will be just like when a prophet passes on the message from his god.”

Quoted with permission from Osborn, Noel D. and Hatton, Howard A. A Handbook on Exodus. (UBS Helps for Translators). New York: UBS, 1999. For this and other handbooks for translators see here .