Charles Ellicott Commentary Exodus 3:20

"And I will put forth my hand, and smite Egypt with all my wonders which I will do in the midst thereof: and after that he will let you go." — Exodus 3:20 (ASV)

I will stretch out my hand. — Hands are stretched out to help and save. God promises here more than He had promised before (Exodus 3:12). He shows how He will “be with” Moses. He will lend him miraculous aid, performing on his behalf “all his wonders,” and with them “smiting the Egyptians.”