On The 7th plague of hail and fire Pharaoh repented and told Moses he would let his people go. At that instant the huge hail balls melted in the air and fell like a soft rain. Why is this? Because the plague was only there to make Pharaoh let the Jewish people go and for the Egyptians to recognize the One and Only G-d. The minute Pharaoh returned to his old ways the Plagued resumed.
