Exodus 4:15–16
15 nYou shall speak to him and oput the words in his mouth, and I will be with your mouth and with his mouth and will teach you both what to do. 16 He shall speak for you to the people, and he shall be your mouth, and you shall be as God to him.
Exodus 4:30
30 Aaron spoke all the words that the Lord had spoken to Moses and did the signs in the sight of the people.