Exodus 8:8

8:8 Then Pharaoh summoned Moses and Aaron and said, “Pray to the Lord that he may take the frogs away from me and my people, and I will release the people that they may sacrifice to the Lord.”

Exodus 8:15

8:15 But when Pharaoh saw that there was relief, he hardened his heart and did not listen to them, just as the Lord had predicted.