Exodus 8:15

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

Exodus 7:4

But Pharaoh will not hearken to you. And I will lay my hand upon Egypt, and bring forth my armies, my people the sons of Israel, out of the land of Egypt by great judgments.

Ecclesiastes 8:11

Because sentence against an evil work is not executed speedily, therefore the heart of the sons of men is fully set in them to do evil.

Exodus 4:21

And LORD said to Moses, When thou go back into Egypt, see that thou do before Pharaoh all the wonders which I have put in thy hand, but I will harden his heart and he will not let the people go.

Exodus 7:13-14

And Pharaoh's heart was hardened, and he did not hearken to them, as LORD had spoken.

Exodus 14:5

And it was told the king of Egypt that the people were fled. And the heart of Pharaoh and of his servants was changed towards the people, and they said, What is this we have done, that we have let Israel go from serving us?

Proverbs 29:1

He who, being often reproved, hardens his neck shall suddenly be destroyed, and that without remedy.

Isaiah 26:10

Let favor be shown to a wicked man, yet he will not learn righteousness. In the land of uprightness he will deal wrongfully, and will not behold the majesty of LORD.

Jeremiah 34:7-11

when the king of Babylon's army was fighting against Jerusalem, and against all the cities of Judah that were left, against Lachish and against Azekah, for these [alone] remained of the cities of Judah, fortified cities.

Hosea 6:4

O Ephraim, what shall I do to thee? O Judah, what shall I do to thee? For your goodness is as a morning cloud, and as the dew that goes away early.

Zechariah 7:11-12

But they refused to hearken, and pulled away the shoulder, and stopped their ears, that they might not hear.

Hebrews 3:8

do not harden your hearts as in the rebellion, according to the day of the trial in the wilderness,

Hebrews 3:15

while it is said, Today if ye will hear his voice, do not harden your hearts as in the rebellion.

Revelation 16:9

And the men were scorched with great heat. And the men blasphemed the name of God who has power over these plagues, and they did not repent to give him glory.

Treasury of Scripture Knowledge

Summary

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

Bible References

He hardened

Exodus 4:21
And LORD said to Moses, When thou go back into Egypt, see that thou do before Pharaoh all the wonders which I have put in thy hand, but I will harden his heart and he will not let the people go.
Exodus 7:4
But Pharaoh will not hearken to you. And I will lay my hand upon Egypt, and bring forth my armies, my people the sons of Israel, out of the land of Egypt by great judgments.
Proverbs 29:1
He who, being often reproved, hardens his neck shall suddenly be destroyed, and that without remedy.
Zechariah 7:11
But they refused to hearken, and pulled away the shoulder, and stopped their ears, that they might not hear.
Hebrews 3:8
do not harden your hearts as in the rebellion, according to the day of the trial in the wilderness,
Revelation 16:9
And the men were scorched with great heat. And the men blasphemed the name of God who has power over these plagues, and they did not repent to give him glory.

General references

Exodus 7:13
And Pharaoh's heart was hardened, and he did not hearken to them, as LORD had spoken.
Exodus 8:32
And Pharaoh hardened his heart this time also, and he did not let the people go.
Jeremiah 34:11
But afterwards they turned, and caused the servants and the handmaids, whom they had let go free, to return, and brought them into subjection for servants and for handmaids.