The first three plagues were unnerving (water to blood, frogs, gnats); the second three were wounding and costly (flies, death of livestock, boils). But the last four plagues would be perilous and devastating.
You may read Exodus 9:13-35 here: Bible Gateway.
Moses repeats God’s command for Pharaoh to let His people go to the desert for a special meeting. But the Lord also adds: The God of the Hebrews is about to release “the full force” of His plagues on Pharaoh, his officials, and the people (vs. 14).
This is the longest warning Pharaoh has received, perhaps because it would also be the most destructive plague so far. For the next day, God would send “the worst hailstorm that has ever fallen on Egypt” (vs. 18) if Pharaoh continues to disregard God’s command.
Some of Pharaoh’s servants are now believers of God. Those who heed Moses’ warning shelter their cattle, (the cattle that wasn’t killed in the fields during the fifth plague.)
True to God’s word, as Moses lifts his staff toward the sky the next day, the worst storm Egypt had ever witnessed breaks loose. Thunder echoes through the land. Hail and lightning not only destroy their crops, but also kill every man and animal in the fields.
“The only place it did not hail was the land of Goshen, where the Israelites were,” (vs. 26).
Although Pharaoh confesses his sin to Moses and said he would release the Israelites, his repentance proves insincere. Moses—knowing Pharaoh wasn’t about to let his people go—grants his request anyway as he prays that the storm would cease.
But Pharaoh “sinned again: He and his officials hardened their hearts . . . He would not let the Israelites go, just as the Lord had said through Moses,” (vs. 34-35).
Reflect

God is merciful and gracious. He doesn’t immediately give sinners what they deserve. Although God gives people second chances, He won’t tolerate persistent, rebellious sin forever.
Moses probably felt like he was running a marathon. Every time he confronts Pharaoh, things just grow worse. But he persists in obeying God anyway. Is there a challenge or conflict that keeps blocking your way? Don’t give up in doing the right thing! As Moses discovers, God rewards persistence.