Exodus 7:13 in the King James Version
And he hardened Pharaoh’s heart, that he hearkened not unto them; as the LORD had said.
Context
12 For they each cast down their rods, and they became serpents; but Aaron’s rod swallowed up their rods.
13 Pharaoh’s heart was hardened, and he didn’t listen to them, as the LORD had spoken.
14 The LORD said to Moses, “Pharaoh’s heart is stubborn. He refuses to let the people go.