Exodus 9:17-9:35
"'Yet you continue to thwart My people, and do not let them go! This time tomorrow I will rain down a very heavy hail, such as has not been in Egypt from the day it was founded until now. Therefore, order your livestock and everything you have in the open brought under shelter; every man and beast that is found outside, not having been brought indoors, shall perish when the hail comes down upon them!'" Those among Pharaoh's courtiers who feared the Lord's word brought their slaves and livestock indoors to safety; but those who paid no regard to the word of the Lord left their slaves and livestock in the open.
The Lord said to Moses, "Hold out your arm toward the sky that hail may fall on all the land of Egypt, upon man and beast and all the grasses of the field in the land of Egypt." So Moses held out his rod toward the sky, and the Lord sent thunder and hail, and fire streamed down to the ground, as the Lord rained down hail upon the land of Egypt. The hail was very heavy--fire flashing in the midst of the hail--such as had not fallen on the land of Egypt since it had become a nation. Throughout the land of Egypt the hail struck down all that were in the open, both man and beast; the hail also struck down all the grasses of the field and shattered all the trees of the field. Only in the region of Goshen, where the Israelites were, there was no hail.
Thereupon Pharaoh sent for Moses and Aaron and said to them, "I stand guilty this time. The Lord is in the right, and I and my people are in the wrong. Plead with the Lord that there may be an end of God's thunder and of hail. I will let you go; you need stay no longer." Moses said to him, "As I go out of the city, I shall spread out my hands to the Lord; the thunder will cease and the hail will fall no more, so that you may know that the earth is the Lord's. But I know that you and your courtiers do not yet fear the Lord God." Now the flax and barley were ruined, for the barley was in the ear and the flax was in bud; but the wheat and the emmer were not hurt, for they ripen late. Leaving Pharaoh, Moses went outside the city and spread out his hands to the Lord: the thunder and the hail ceased, and no rain came pouring down upon the earth. But when Pharaoh saw that the rain and the hail and the thunder had ceased, he became stubborn and reverted to his guilty ways, as did his courtiers. So Pharaoh's heart stiffened and he would not let the Israelites go, just as the Lord had foretold through Moses.