Exodus 4:14-17

14Then the anger of the Lord was kindled against Moses and he said, "Is there not Aaron, your brother, the Levite? I know that he can speak well. Behold, he is coming out to meet you, and when he sees you, he will be glad in his heart.

15You shall speak to him and put the words in his mouth, and I will be with your mouth and with his mouth and will teach you both what to do.

16He shall speak for you to the people, and he shall be your mouth, and you shall be as God to him.

17And take in your hand this staff, with which you shall do the signs."