NOTES for Exo 4:13
How does a person become a prophet? One could say that nothing here depends on the person, that this is God's business, and that the person becomes a prophet whom God makes a prophet. But the matter is arranged somewhat differently.
God calls Moses to His service. He sees in Moses a prophet, His servant, to whom He entrusts a difficult and responsible mission: to lead His people out of Egypt so that He may then make a covenant with them, beginning a new era both in His relationship with them and in their history.
But Moses hesitates. He resists as much as he can. He says directly to God: send someone else, whomever You can find. He does not doubt that God can find someone else. He does not doubt God at all. He doubts himself.
But Moses also does not doubt that the One speaking with him is none other than the God of his fathers. Why then does he distrust himself so much? Perhaps precisely because he knows a good deal about the God of his fathers? He knows, among other things, what "real" prophets are like. Oh yes, of course, they are not like him: from their youth they live apart from people, God speaks with them constantly, they know what prophetic ecstasy is, what inspired prophetic preaching is... But Moses knows none of this; he cannot speak as prophets speak ("I am slow of speech," Moses says of himself to God).
In short, Moses thinks of himself as the "wrong" kind of prophet. Send someone else, he says to God. Well then, there will be someone else too: to help Moses, God will send a "real" one, Aaron. And yet it is God who makes a prophet a prophet. And by no means always according to human patterns.