Exodus 4:10-16 NIV
Moses said to the LORD, “Pardon your servant, Lord. I have never been eloquent, neither in the past nor since you have spoken to your servant. I am slow of speech and tongue.”
The LORD said to him, “Who gave human beings their mouths? Who makes them deaf or mute? Who gives them sight or makes them blind? Is it not I, the LORD? Now go; I will help you speak and will teach you what to say.”
But Moses said, “Pardon your servant, Lord. Please send someone else.”
Then the LORD’s anger burned against Moses and he said, “What about your brother, Aaron the Levite? I know he can speak well. He is already on his way to meet you, and he will be glad to see you. You shall speak to him and put words in his mouth; I will help both of you speak and will teach you what to do. He will speak to the people for you, and it will be as if he were your mouth and as if you were God to him.
NIV: New International Version