Exodus 9:14
For I will at this time send all my plagues upon thine heart, and upon thy servants, and upon thy people; that thou mayest know that there is none like me in all the earth. For I will at this time send all my plagues upon thine heart, and upon thy servants, and upon thy people; that thou mayest know that there is none like me in all the earth.
God will at this time send all His plagues upon Pharaoh's heart and upon his servants and upon his people, so that Pharaoh may know that there is none like God in all the earth. The plagues were sent to make Pharaoh and Egypt know that no one is like the Lord. The phrase at this time signals an escalation to heavier, more severe judgments, specifically a very grievous hail such as had not been in Egypt since its foundation. Every rejected punishment would be followed by one more severe until his proud heart was humbled to acknowledge the Maker of heaven and earth as the true and living God.
God told Moses beforehand that Pharaoh would not yield until judgments were visited upon Egypt and Israel was brought out by a signal manifestation of power. Before each plague its nature and effects were described to the king so he could save himself from it if he chose. The plagues were announced beforehand so they could not be dismissed as chance.
In mercy in the midst of judgment God gave warning to gather cattle and all that was in the field into shelter, because man and beast left in the field would die. The warning gave those who heeded God's word a chance to protect their people and cattle and provided a way of escape for all who heeded it. The offer of escape tested the pride of the Egyptians and revealed whose hearts were really affected by God's dealings with His people. Those who feared the word of the Lord made their servants and cattle flee into houses, while those hardened like Pharaoh left them in the field.
The resulting hailstorm of thunder and lightning with fire mingled with hail smote man, beast, herb and tree throughout Egypt. The hailstorm of thunder and fire mingled with hail destroyed herbs, trees, man and beast, while the land of Goshen where Israel was alone was spared. The hail and fire with thunder and lightning demonstrated that the whole earth is under the command of the God of the Hebrews and that even the elements obey His voice.
Pharaoh was humbled by the hail, confessed that he and his people had sinned, and asked for intercession. Yet when the plague was stayed he continued to resist and refused to let Israel go, his continual opposition hardening his whole being in rebellion against divine power. Providence had placed Pharaoh on the throne at the appointed time for Israel's deliverance, and God had not given him life in order to use him for this purpose. Though Pharaoh had forfeited mercy through his crimes, God preserved his life so that his stubborn resistance would display divine power and wonders in Egypt.
The plagues punish the people of Egypt for idolatry, showing God's hatred of idolatry and His determination to punish cruelty and oppression. They expose how vain is the wisdom of their mighty men and how feeble the power of their gods when opposed to the commands of Jehovah, and silence their boasting of blessings received from senseless deities. God sends the plagues to glorify His own name, so that other nations may hear of His power and tremble at His mighty acts, and so that His people may be led to turn from idolatry and render Him pure worship. The only true safety for nations and individuals is obedience to God's voice and standing for truth and righteousness.