Overall, the Bible's usage conforms most closely to the Greek usage, that a prophet is one who speaks for another. As we will see, it is not limited to God. In this situation, Moses' and Aaron's relationship is analogous to God's and Moses'.
Moses is quite instructive in regard to our feelings about ourselves. We say, "What can I do? I'm so weak. I have no abilities." Moses said, "I am not a man of words." Was he not already justifying himself? He said, "I am heavy of mouth and tongue." (KJV) This is not exactly stammering, as some believe, but he is saying that he did not have a gift of speech. He means that he did not have it by nature, and that he did not have it developed within him since God began speaking to him. This is the same man about whom Stephen, who was defending himself against the Jews in Acts 7, said the following:
Is there a contradiction here? No, there is not. Both Moses and Stephen were correct. Moses was correct about himself. He did not have the gift of speaking, and he was not an eloquent man. Stephen was also correct. This is showing us that the power, the effectiveness in Moses' words was not in Moses himself but was in what God added to the words that came out of Moses' mouth. It was God who made the impact on the hearer's mind.
I would have to guess, to speculate, that in one sense this was never really overcome in Moses, that he was not eloquent as men would count eloquence. But yet what he said had awesome power because of God being in what he said. And so both men were correct—Moses about himself and Stephen seeing it from his perspective. Moses really said powerful things because God added to what Moses actually said. We have to remember this.
As you can see, in verse 14 God became angry at Moses' resistance, but really at Moses' unbelief is what it amounts to. God's promise to be with him did not mean that Moses would suddenly become eloquent and fluent. We have to understand that God knows how to use His creatures. He will use them to His end. If a man has great resources, his sufficiency makes God unnecessary, and he becomes puffed up. So God makes clear, through Paul, that He purposely calls the weak for His end.
This is what I mean when I said this is not limited to God and men, but also takes place from one man to another. Aaron was Moses' prophet, and Moses was God's prophet.
What is beginning to become clear here is that the prophet is a message-carrier from one of greater authority. In this case Moses was in the position of God to Aaron, and Moses thus was also in the position of God to Pharaoh.
By combining Exodus 4 with Exodus 7, the biblical usage of a prophet has a good foundation. It begins to become clear that a prophet is one who expresses the will of God in words, and sometimes with signs given to confirm what was said.
In our thoughts, let's go back to Moses—first in that situation in Exodus 4 to get a little more background. God not only initiated the calling of Moses, but He also initiated his birth and the preservation of his life. In addition to that, it was God who gifted him with the mind that he had to enable him to take advantage of the magnificent education he received, but God also left Moses with a flaw in his speaking ability.
We might question why that occurred, and we can say that maybe God wanted Moses to be humbled in some regard. It was this that gave rise to the startling statement in Exodus 4:10-11 regarding God's involvement in providing some people with other deficiencies. John 9:3 is a confirmation from Jesus that indeed this does occur. It was God who made that man in John 9:3 to be born blind. Nobody sinned. God caused the man to be born blind. This is admitted very plainly by God in Exodus 4:11, which says: "Who has made man's mouth? or who makes the dumb, or deaf, or the seeing, or the blind? Have not I the LORD?"
Moses engaged in this pattern of twisted thinking when God asked him to be a spokesman
Now there is certainly a time and place for genuine humility. Humility is a godly trait. But feigned humility or self-deprecation is not appropriate to make light of a spiritual or physical gift that has freely given us.
