“And Pharaoh hardened his heart at this time also, neither would he let the people go.”
Exodus 8:32 (KJV)
Context Reading
30And Moses went out from Pharaoh, and intreated the LORD. 31And the LORD did according to the word of Moses; and he removed the swarms of flies from Pharaoh, from his servants, and from his people; there remained not one. 32And Pharaoh hardened his heart at this time also, neither would he let the people go.