Shemot 4:10-16

And Moshe said unto HASHEM, O Adonoi, I am not an ish devarim, neither heretofore, nor since Thou hast spoken unto Thy eved; but I am slow of speech, and of a slow lashon. And HASHEM said unto him, Who hath made manʼs peh (mouth)? Or who maketh dumb, or deaf, or seeing, or blind? Is it not I, HASHEM? Now therefore go, and Eh-heh-yeh (I will be) with thy mouth, and teach thee what thou shalt say. And he said, O Adonoi, send, now, by the yad of him whom Thou wilt send. And the Af HASHEM was kindled against Moshe, and He said, Is there not Aharon thy ach the Levi? I know that he can speak well. And also, hinei, he cometh forth to meet thee; and when he seeth thee, he will be glad in his lev. And thou shalt speak unto him, and put words in his mouth; and Eh-heh-yeh (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 he shall be, even he shall be to thee instead of a mouth, and thou shalt be to him instead of Elohim.