Exodus 10:17
Now therefore forgive, I pray thee, my sin only this once, and intreat the LORD your God, that he may take away from me this death only. Now therefore forgive, I pray thee, my sin only this once, and intreat the LORD your God, that he may take away from me this death only.
The death Pharaoh begged to have taken away was the locust plague itself, brought by an east wind over all Egypt. The locusts covered the face of the whole land and darkened it, eating every herb of the land and all the fruit of the trees left by the hail until no green thing remained in tree or field. The Egyptians feared the locusts would next attack and devour the people themselves, and the dreadful plague sent by the Lord nearly destroyed Egypt.
Pharaoh spoke when, under threat of death, he hastily called and sent for Moses and Aaron. He confessed that he had sinned against the Lord and against Moses and Aaron, and asked forgiveness only this once, once more. He asked them to entreat and pray to the Lord his God to take away from him this death, the deadly plague of locusts. Moses went out from Pharaoh and prayed, and the Lord sent a mighty strong west wind that carried away all the locusts into the Red Sea, so that not one locust remained in all Egypt.
Moses and Aaron had told Pharaoh beforehand the nature and effect of each plague that would follow his refusal to let Israel go, and every plague came exactly as told. In that setting the locust plague exposed the impotence of Serapis, whom the Egyptians trusted to protect them from locusts, teaching that protection comes from Jehovah and not from an idol. The plea reveals a proud and idolatrous king very slow to yield to the requirements of the God of Heaven, who chose to receive the plagues rather than submit to God and without remorse watched his whole kingdom lie under dreadful judgments. Even under most grievous affliction he yielded only a little, granting that the children and wives might go but refusing to let the cattle go, doing no more than he was compelled to do by the visitations of wrath.
His plea was limited to that occasion and sought relief from punishment, not a lasting change of heart. His sorrow was over the painful consequences of his hardness of heart, not a sincere repentance that submitted his proud will to God. His humility lasted only while death threatened him, and when the affliction was removed he did not remain humble but hardened his heart. He broke his humble promise and returned to rebellion, persisting in his stubborn decision and refusing to let Israel go even after Egypt was ruined, and the Lord hardened his heart.