Exodus 8:15

And Pharaoh saw that there was respite; and he hardened his heart, and hearkened not to them, as Jehovah had said.

Exodus 7:4

And Pharaoh will not hearken unto you; and I will lay my hand upon Egypt, and bring forth my hosts, my people, the children 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 children of men is fully set in them to do evil.

Exodus 4:21

And Jehovah said to Moses, When thou goest to return to Egypt, see that thou do all the wonders before Pharaoh that I have put in thy hand. And I will harden his heart, that he shall not let the people go.

Exodus 7:13-14

And Pharaoh's heart was stubborn, and he hearkened not to them, as Jehovah had said.

Exodus 14:5

And it was told the king of Egypt that the people had fled; and the heart of Pharaoh and of his bondmen was turned against the people, and they said, Why have we done this, that we have let Israel go from our service?

Proverbs 29:1

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

Isaiah 26:10

If favour be shewn to the wicked, he doth not learn righteousness: in the land of uprightness he dealeth unjustly, and beholdeth not the majesty of Jehovah.

Jeremiah 34:7-11

And the king of Babylon's army fought against Jerusalem, and against all the cities of Judah that were left, against Lachish, and against Azekah; for these were amongst the cities of Judah, the fenced cities that were left.

Hosea 6:4

What shall I do unto thee, Ephraim? What shall I do unto thee, Judah? For your goodness is as a morning cloud, and as the dew that early passeth away.

Zechariah 7:11-12

But they refused to hearken, and turned a rebellious shoulder, and made their ears heavy, that they should not hear.

Hebrews 3:8

harden not your hearts, as in the provocation, in the day of temptation in the wilderness;

Hebrews 3:15

in that it is said, To-day if ye will hear his voice, do not harden your hearts, as in the provocation;

Revelation 16:9

And the men were burnt with great heat, and blasphemed the name of God, who had authority over these plagues, and 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 Jehovah said to Moses, When thou goest to return to Egypt, see that thou do all the wonders before Pharaoh that I have put in thy hand. And I will harden his heart, that he shall not let the people go.
Exodus 7:4
And Pharaoh will not hearken unto you; and I will lay my hand upon Egypt, and bring forth my hosts, my people, the children of Israel, out of the land of Egypt by great judgments.
Proverbs 29:1
He that being often reproved hardeneth his neck, shall suddenly be destroyed, and without remedy.
Zechariah 7:11
But they refused to hearken, and turned a rebellious shoulder, and made their ears heavy, that they should not hear.
Hebrews 3:8
harden not your hearts, as in the provocation, in the day of temptation in the wilderness;
Revelation 16:9
And the men were burnt with great heat, and blasphemed the name of God, who had authority over these plagues, and did not repent to give him glory.

General references

Exodus 7:13
And Pharaoh's heart was stubborn, and he hearkened not to them, as Jehovah had said.
Exodus 8:32
And Pharaoh hardened his heart this time also, and would not let the people go.
Jeremiah 34:11
But afterwards they turned, and caused the bondmen and the bondmaids whom they had let go free, to return, and brought them into subjection for bondmen and for bondmaids.