Egyptian texts about the Pharaoh speak about his power as his strong hand; he destroys enemies with his arm. Here God says his hand will defeat the Pharaoh. As is written in Psalm 2:4–5: He who sits in the heaven laughs; the Lord holds them in derision. Then he will speak to them in his wrath, and terrify them in his fury.
20 So I will stretch out my hand and strike Egypt with all the wonders that I will do in it; after that he will let you go.