Exodus 9:27-35

Then Pharaoh sent and called Moses and Aaron and said to them, “This time I have sinned; the LORD is in the right, and I and my people are in the wrong. Plead with the LORD, for there has been enough of God’s thunder and hail. I will let you go, and you shall stay no longer.” Moses said to him, “As soon as I have gone out of the city, I will stretch out my hands to the LORD. The thunder will cease, and there will be no more hail, so that you may know that the earth is the LORD’s. But as for you and your servants, I know that you do not yet fear the LORD God.” (The flax and the barley were struck down, for the barley was in the ear and the flax was in bud. But the wheat and the emmer were not struck down, for they are late in coming up.) So Moses went out of the city from Pharaoh and stretched out his hands to the LORD, and the thunder and the hail ceased, and the rain no longer poured upon the earth. But when Pharaoh saw that the rain and the hail and the thunder had ceased, he sinned yet again and hardened his heart, he and his servants. So the heart of Pharaoh was hardened, and he did not let the people of Israel go, just as the LORD had spoken through Moses.