And the LORD said to Moses, Go in to Pharaoh: for I have hardened his heart, and the heart of his servants; that I might show these my signs before him:

Yes, 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.

He refuseth

And I say to thee, Let my son go, that he may serve me: and if thou shalt refuse to let him go, behold, I will slay thy son, even thy first-born.

And if thou shalt refuse to let them go, behold, I will smite all thy borders with frogs:

For if thou shalt refuse to let them go, and wilt hold them still,

Else, if thou shalt refuse to let my people go, behold, to-morrow will I bring the locusts into thy border:

But if ye refuse and rebel, ye shall be devoured with the sword: for the mouth of the LORD hath spoken it.

Why then hath this people of Jerusalem slidden back by a perpetual backsliding? they hold fast deceit, they refuse to return.

Thy habitation is in the midst of deceit; through deceit they refuse to know me, saith the LORD.

See that ye refuse not him that speaketh. For if they escaped not who refused him that spoke on earth, much more shall not we escape, if we turn away from him that speaketh from heaven:

General references

And Pharaoh hardened his heart at this time also, neither would he let the people go.

And the LORD hardened the heart of Pharaoh, and he hearkened not to them; as the LORD had spoke to Moses.

But the LORD hardened Pharaoh's heart, so that he would not let the children of Israel go.