Charles Spurgeon Commentary Exodus 10:18-20

"And he went out from Pharaoh, and entreated Jehovah. And Jehovah turned an exceeding strong west wind, which took up the locusts, and drove them into the Red Sea; there remained not one locust in all the border of Egypt. But Jehovah hardened Pharaoh`s heart, and he did not let the children of Israel go." — Exodus 10:18-20 (ASV)

God kept his grace back from him, so that he relapsed into his natural state of obduracy. Pharaoh is the great mirror of pride and obstinacy; I wonder whether we have a Pharaoh here.