Exodus 4:14-17

And the anger of Jehovah was kindled against Moses, and he said, Is there not Aaron thy brother the Levite? I know that he can speak well. And also, behold, he cometh forth to meet thee: and when he seeth thee, he will be glad in his heart. And thou shalt speak unto him, and put the words in his mouth: and I will be with thy mouth, and with his mouth, and will teach you what ye shall do. And he shall be thy spokesman unto the people; and it shall come to pass, that he shall be to thee a mouth, and thou shalt be to him as God. And thou shalt take in thy hand this rod, wherewith thou shalt do the signs.