Exodus 14:4

And the LORD said unto Moses, When thou goest to return into Egypt, see that thou do all those wonders before Pharaoh, which I have put in thine hand: but I will harden his heart, that he shall not let the people go. And thou shalt say unto Pharaoh, Thus saith the LORD, Israel is my son, even my firstborn: And I say unto thee, Let my son go, that he may serve me: and if thou refuse to let him go, behold, I will slay thy son, even thy firstborn. And it came to pass by the way in the inn, that the LORD met him, and sought to kill him. Then Zipporah took a sharp stone, and cut off the foreskin of her son, and cast it at his feet, and said, Surely a bloody husband art thou to me. So he let him go: then she said, A bloody husband thou art, because of the circumcision. And the LORD said to Aaron, Go into the wilderness to meet Moses. And he went, and met him in the mount of God, and kissed him. And Moses told Aaron all the words of the LORD who had sent him, and all the signs which he had commanded him. And Moses and Aaron went and gathered together all the elders of the children of Israel: And Aaron spake all the words which the LORD had spoken unto Moses, and did the signs in the sight of the people. And the people believed: and when they heard that the LORD had visited the children of Israel, and that he had looked upon their affliction, then they bowed their heads and worshipped.

And I will harden Pharaoh's heart, and multiply my signs and my wonders in the land of Egypt.

And the LORD hardened the heart of Pharaoh king of Egypt, and he pursued after the children of Israel: and the children of Israel went out with an high hand.

(According as it is written, God hath given them the spirit of slumber, eyes that they should not see, and ears that they should not hear;) unto this day.