Exodus 10:19
And the LORD turned a mighty strong west wind, which took away the locusts, and cast them into the Red sea; there remained not one locust in all the coasts of Egypt. And the LORD turned a mighty strong west wind, which took away the locusts, and cast them into the Red sea; there remained not one locust in all the coasts of Egypt.
The locusts had darkened the land and eaten every herb and all the fruit left by the hail until no green thing remained in tree or field, and the Egyptians feared they would next attack and devour the people themselves. Pharaoh hastily summoned Moses and Aaron, confessed he had sinned against God and against them, asked forgiveness only this once, and begged them to entreat God to take away this death. Moses and Aaron prayed to the Lord and entreated Him at Pharaoh's request.
In answer the Lord turned a mighty strong wind from the west that took away the locusts and cast them into the Red Sea, so that not one locust remained in all the coasts of Egypt. Their coming at Moses' command and departing at his bidding shows that Jehovah alone has power over the locusts. Their removal exposed the impotence of Serapis, worshiped as the protector of the land from locusts, and taught Egypt not to trust in any protection other than Jehovah.
The locust plague was a dreadful judgment sent by the Lord upon Egypt because Pharaoh refused to submit to God and chose to receive the plagues instead. Pharaoh watched without remorse as his whole kingdom came under the miracle of these dreadful judgments, which nearly destroyed and ruined Egypt. Moses and Aaron had told Pharaoh beforehand the nature and effect of each plague, and each came exactly as they said it would come, yet Pharaoh would not yield.
Pharaoh humbled himself and promised to let Israel go only while death threatened him, yielding only a little and only as much as he was compelled to, and when the affliction was removed he took back what he had granted. After the locusts were removed Pharaoh refused to let the children of Israel go and remained stubborn. After his relief the Lord hardened Pharaoh's heart so that he would not let Israel go. After his relief Pharaoh hardened his own heart again.
His concession after the locusts was to let the children and wives go also, but he would not let the cattle go. The removal of the locusts was followed by the plague of darkness, and because Pharaoh still persisted in rebellion Moses told him next that the angel of God would slay the firstborn.