Commentary for Exodus 4:16

ודבר הוא לך means HE WILL SPEAK to the people ON THY ACCOUNT (לְךָ). This passage is proof, regarding every usage of לך and לי and לו and לכם and להם that follow after the verb דבר, that they all have the meaning of על “on account of”.

ודבר הוא לך, he will do the speaking on your behalf.

לאלוהים, so that he will perform miracles at your behest.

ודבר הוא לך אל העם, “and he will speak on your behalf to the people;” Ibn Ezra writes that this was not a demotion of some kind for Moses, but the very reverse. Aaron’s role in this is to be compared to the role of the mouth of a person which represents the thoughts of that person’s soul. The soul, by definition, is not visible, just as the angels are not visible, seeing they have no body. Moses therefore had been elevated to the stature of an angel by having Aaron as his interpreter. This is how we can understand G’d saying that Moses would be to Aaron similar to אלוקים. The word אלוקים throughout Scripture is a name symbolizing the majesty of G’d or that of His holy angels. The angels are the ones who familiarize us with what G’d is doing at certain times during our history. At any rate, Aaron, far from being demoted to being a mere “mouthpiece,” had been promoted to reveal the invisible thoughts of Moses, i.e. of what G’d had communicated to him.

This is an indication. In other words, this verse is one of the indicators. For Rashi has many other verses to prove that these words mean על , which denotes בשביל (for). [The proof here is that] if לך is to be taken literally, then it means that Aharon will speak to Moshe. If so, what does “to the people,” which follows it, mean? Therefore it must mean “for you,” i.e., “in place of you.”

יהיה לך לפה HE SHALL BE TO THEE INSTEAD OF A MOUTH — he will be to thee as a spokesman because thou art slow of speech (Exodus Rabbah 3:17).

תהיה לו לאלוהים, you will act as his superior, instructing him in what to do.

לאלהים means a superior and chief (cf. Onkelos).