Exodus 8:15

But when Pharaoh saw that there was relief, he hardened his heart and would not listen to Moses and Aaron, just as the LORD had said.

(New International Version)

But when Pharaoh saw that there was relief, he hardened his heart and did not listen to them, as the LORD had said.

(New American Standard Bible)

But when Pharaoh saw that there was respite, he hardened his heart, and hearkened not unto them; as the LORD had said.

(King James Version)