and Aaron relayed everything the LORD had said to Moses. And Moses performed the signs before the people,

Exodus 4:1
Then Moses answered, "What if they do not believe me or listen to my voice? For they may say, 'The LORD has not appeared to you.'"

Exodus 4:15
You are to speak to him and put the words in his mouth. I will help both of you to speak, and I will teach you what to do.

Exodus 4:16
He will speak to the people for you. He will be your spokesman, and it will be as if you were God to him.

Exodus 19:7
So Moses went back and summoned the elders of the people and set before them all these words that the LORD had commanded him.

And Aaron spoke all the words which the LORD had spoken to Moses, and did the signs in the sight of the people.