Exodus 8:28-32

28Pharaoh said, “1I will let you go, so that you may sacrifice to the Lord your God in the wilderness; only you shall not go very far away. 2Plead for me.” 29Then Moses said, “Behold, I am going to leave you, and I will plead with the Lord that the swarms of flies may depart from Pharaoh, from his servants, and from his people tomorrow; only do not let Pharaoh 3deal deceitfully again in not letting the people go to sacrifice to the Lord.”

30So 4Moses left Pharaoh and pleaded with the Lord. 31The Lord did 5as Moses asked, and removed the swarms of flies from Pharaoh, from his servants, and from his people; not one remained. 32But Pharaoh 6hardened his heart this time also, and 7he did not let the people go.