Exodus 7:14
“And the Lord said unto Moses, Pharaoh’s heart is hardened, he refuseth to let the people go.”
For they cast down every man his rod, and they became serpents: but Aaron’s rod swallowed up their rods.
And he hardened Pharaoh’s heart, that he hearkened not unto them; as the Lord had said.
And the Lord said unto Moses, Pharaoh’s heart is hardened, he refuseth to let the people go.
Get thee unto Pharaoh in the morning; lo, he goeth out unto the water; and thou shalt stand by the river’s brink against he come; and the rod which was turned to a serpent shalt thou take in thine hand.
And thou shalt say unto him, The Lord God of the Hebrews hath sent me unto thee, saying, Let my people go, that they may serve me in the wilderness: and, behold, hitherto thou wouldest not hear.
Counter-Arguments
The strongest case that this verse does not belong in this theme.

Cross-References
“But the Lord hardened Pharaoh’s heart, and he would not let them go.”
“Yea, they made their hearts as an adamant stone, lest they should hear the law, and the words which the Lord of hosts hath sent in his spirit by the former prophets: therefore came a great wrath from the Lord of hosts.”
“See that ye refuse not him that speaketh. For if they escaped not who refused him that spake on earth, much more shall not we escape, if we turn away from him that speaketh from heaven:”
“But the Lord hardened Pharaoh’s heart, so that he would not let the children of Israel go.”
“Else, if thou refuse to let my people go, behold, to morrow will I bring the locusts into thy coast:”