15 You shall speak to him and put words in his mouth; I will help both of you speak and will teach you what to do.

Read Exodus 4:15 Using Other Translations

And thou shalt speak unto 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.
You 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.
Talk to him, and put the words in his mouth. I will be with both of you as you speak, and I will instruct you both in what to do.