"Then the LORD said to Moses, 'Rise early in the morning and stand before Pharaoh, and say to him, 'Thus says the LORD God of the Hebrews: "Let My people go, that they may serve Me, for at this time I will send all My plagues to your very heart, and on your servants and on your people, that you may know that there is none like Me in all the earth. Now if I had stretched out My hand and struck you and your people with pestilence, then you would have been cut off from the earth. But indeed for this purpose I have raised you up, that I may show My power in you, and that My name may be declared in all the earth. As yet you exalt yourself against My people in that you will not let them go"'" (Exo. 9:13-17).
God had already struck their animals in the field with a pestilence and destroyed them. If He directed such against the Egyptian people, it would annihilate them. It wasn't God's purpose to wipe the Egyptians off the face of the map but to show His power and glorify His name through all the Earth through Pharaoh's stubbornness. These final plagues will really strike at the heart of Pharaoh.
God has another plague in store for the rebellious leader. Moses announces when it will happen and even explains (via the mercy of God) what must be done to survive it - "Behold, tomorrow about this time I will cause very heavy hail to rain down, such as has not been in Egypt since its founding until now. Therefore send now and gather your livestock and all that you have in the field, for the hail shall come down on every man and every animal which is found in the field and is not brought home; and they shall die" (9:18,19). The damage inflicted by the hail would be extensive and greater than anything they had seen before caused by hail. Anything caught outside in the fierce storm would perish.
"He who feared the word of the LORD among the servants of Pharaoh made his servants and his livestock flee to the houses. But he who did not regard the word of the LORD left his servants and his livestock in the field" (9:20,21). Here we have the first glimpse of respect toward Jehovah by at least some of the Egyptian people. It wasn't just Pharaoh that was suffering from these plagues; his people were enduring them, too. No doubt it was common knowledge as to why these afflictions kept coming. Those who were reasonable heeded Moses' warning and moved their animals and servants inside before the hailstorm. Others foolishly chose to disbelieve. They would regret this decision later.
Moses, at God's command, then stretched out his hand toward heaven. "And the LORD sent thunder and hail, and fire darted to the ground. And the LORD rained hail on the land of Egypt. So there was hail, and fire mingled with the hail, so very heavy that there was none like it in all the land of Egypt since it became a nation" (9:23,24). The damage caused was extensive and unlike any of them had seen before. Besides animals perishing, the trees were broken and the early crops (flax and barley) were destroyed by the hail. The late crops (wheat and spelt) were not harmed, however, and some trees also survived for the next plague. Where was Shu, the Egyptian wind god, during this storm? Where was Nut, the sky goddess? The plague originated in her domain yet she did nothing to stop it! And then there were the destroyed fields Iris and Seth were supposed to protect. The Egyptians are getting a well-rounded education regarding the impotence of their gods!
As before, this plague did not affect the Israelites. There was no hail in the land of Goshen! There is only one true and living God, Jehovah! Pharaoh become desperate again for relief and called for Moses and Aaron - "I have sinned this time. The LORD is righteous, and my people and I are wicked. Entreat the LORD, that there may be no more mighty thundering and hail, for it is enough. I will let you go, and you shall stay no longer" (9:27,28). Moses agrees to do so, though he knows that after relief comes Pharaoh will "not yet fear the LORD God" (9:30). This is precisely the case, sadly. Pharaoh breaks his third promise. Even his repentance is noticeably shallow ("I have sinned this time"). Eventually Pharaoh will let the people go, though he has chosen to bring much more pain and destruction upon himself and his people first.