Exodus 4:15

And thou shalt speak unto him, and put words in his mouth,.... Or "things" z, the matter and substance of what he should say, who being a man of words, an eloquent man, and a good spokesman, would put them into proper language, and express them fluently:

and I will be with thy mouth, and with his mouth, and will teach you what ye shall do; or speak what Moses should say to Aaron, and what Aaron should say to Pharaoh, and to the people of Israel; so that as Aaron was under Moses, and at his direction, they were both dependent on the Lord, and under his direction; and the one, as well as the other, needed his assistance, even Aaron that could speak well. Moses furnished him with matter, he put it into words, and both were instructed and influenced by the Lord what they should say and do.

z את הדברים.