Exodus 4:14-17

14And the anger of the LORD was kindled against Moses, and he said, Is not Aaron the Levite thy brother? 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. 15And thou shalt speak to him, and put words in his mouth: and I will be with thy mouth, and with his mouth, and will teach you what ye shall do. 16And he shall speak for thee to the people: and he shall be, even he shall be to thee instead of a mouth, and thou shalt be to him instead of God. 17And thou shalt take this rod in thy hand, with which thou shalt perform signs.