V.1-7 God was going to bring Israel out of Egypt “by great judgments” (punishments).
V.4 If Pharaoh the king acts harshly toward Israel, he would get the same treatment in return (compare Gen. 12:3 and Gal. 6:7).
V.3 Some might think that God hardened Pharaoh’s heart first, but this is not so. Pharaoh hardened it first (Ex. 5:2), although God does tell us beforehand that He knew he would refuse to let the Israelites go out of Egypt (Ex. 3:19).
V.8-13 People like to see miracles, but their hearts are not changed by such acts of power. It was the same when Jesus was down here (John 2:23-25; John 6:25-29).
V.14-25 The Lord begins His great punishments over the whole land of Egypt. But men under the power of Satan (v. 22), also do great things, and the king continues not listening to the Lord. Pharaoh was so hard-hearted (v. 23) that he does not even feel disturbed by the troubles of his own people as they search for water to drink. It was the Lord in His mercy Who stopped this first punishment (v. 25).