Rather than inspiring confidence in Moses, God"s commission frightened him ( Exodus 4:10-12). Moses" claim to be slow of speech (not handicapped, but lacking in eloquence) was a thinly veiled excuse by which Moses hoped to escape his calling. Stephen said Moses was eloquent ( Acts 7:22). Apparently Moses felt he did not have sufficient oratorical ability to persuade the Israelite elders or Pharaoh. God assured Moses that He would enable Him to communicate effectively. Again God reminded Moses that He was the creator. [source][source][source]
"This claim of inadequacy is a recurring one in OT passages having to do with God"s call and commission (cf, e.g, Judges 6:14-15; 1 Samuel 10:20-24; 1 Kings 3:5-9; Isaiah 6:5-8; Jeremiah 1:4-10; see also Habel ... [1] Whatever its connection to prophetic and royal traditions of the word and the messenger, its more important rootage is in the OT pattern of the weak become strong, the least become great, the mean become mighty, the last become first (cf, e.g, Judges 6:11-24; 1 Samuel 16:1-13; 1 Samuel 17:19-54; Amos 7:14-15; Isaiah 6:1-13; Jeremiah 1:4-19; and even Isaiah 52:13 to Isaiah 53:12). This pattern is a metaphor of theological assertion in the Bible, and everywhere it occurs, its fundamental message is the same: God"s word, God"s rule, God"s teaching, God"s deliverance come not from Prayer of Manasseh , no matter who that man may be, but from God. Even the election of Israel makes this point. Indeed that election is probably the most convincing of all the occurrences of the pattern." [2][source]
"Cherish the lowliest thought you choose of yourself, but unite it with the loftiest conception of God"s All-Sufficiency. Self-depreciation may lead to the marring of a useful life. We must think soberly of ourselves, not too lowly, as not too extravagantly. The one talent must not be buried in the earth." [3][source]
Unable to excuse himself, Moses finally admitted that he did not want to obey God ( Exodus 4:13-16). God became angry with Moses because he refused to obey. However, the sovereign Lord would not let His reluctant servant go (cf. Jonah). Instead He provided a mouthpiece for Moses in his older brother by three years, Aaron (cf. Exodus 7:7). This act was both an aid to Moses and a discipline for his disobedience. On the one hand Aaron was an encouragement to Moses, but on the other he proved to be a source of frustration as a mediator (e.g, ch32). [source][source][source]
"The mouth of Moses may well be heavy and clumsy, slow and halting in speech. It would not matter if it were dumb altogether, and Aaron"s mouth, as well. Yahweh will be there, and Yahweh will take responsibility for both the message and the messengers. The staff in the hands of Moses and Aaron is a symbol of this powerful Presence." [4][source]
As time passed, Moses grew more confident and communicative and increasingly took his proper place as Israel"s leader. [source][source][source]