Exodus 9:28

9:28 Pray to the Lord, for the mighty thunderings and hail are too much! I will release you and you will stay no longer.”

Exodus 9:34-35

9:34 When Pharaoh saw that the rain and hail and thunder ceased, he sinned again: both he and his servants hardened their hearts. 9:35 So Pharaoh’s heart remained hard, and he did not release the Israelites, as the Lord had predicted through Moses.