Exodus 10:16-20 (KJV)
16 Then Pharaoh called for Moses and Aaron in haste; and he said, I have sinned against the Lord your God, and against you.
17 Now therefore forgive, I pray thee, my sin only this once, and intreat the Lord your God, that he may take away from me this death only.
18 And he went out from Pharaoh, and intreated the Lord.
19 And the Lord turned a mighty strong west wind, which took away the locusts, and cast them into the Red sea; there remained not one locust in all the coasts of Egypt.
20 But the Lord hardened Pharaoh’s heart, so that he would not let the children of Israel go.