Exodus 5:2

5:2 But Pharaoh said, “Who is the Lord that I should obey him by releasing Israel? I do not know the Lord, and I will not release Israel!”

Exodus 8:21

8:21 If you do not release my people, then I am going to send swarms of flies on you and on your servants and on your people and in your houses. The houses of the Egyptians will be full of flies, and even the ground they stand on.

Exodus 11:1

The Tenth Blow: Death

11:1 The Lord said to Moses, “I will bring one more plague on Pharaoh and on Egypt; after that he will release you from this place. When he releases you, he will drive you out completely from this place.