Exodus 8:15

And Pharaoh will see that there was enlargement, and he made his heart heavy, and he heard not to them; as Jehovah spake.

Exodus 7:4

And Pharaoh will not hear to you; and I gave ray hand upon Egypt, and I brought forth my army, my people the sons of Israel, out of Egypt, with great judgments.

Ecclesiastes 8:11

Because a decree was not done quickly upon an evil work, for this the heart of the sons of man was filled in them to do evil.

Exodus 4:21

And Jehovah will say to Moses, In thy going to turn back to Egypt, see all the wonders which I put in thy hand: do them before Pharaoh; and I will bind fast his heart and he shall not send forth the people.

Exodus 7:13-14

And Pharaoh's heart. will be strengthened, and he will not hear to them; as Jehovah said.

Exodus 14:5

And it was announced to the king of Egypt that the people fled: and the heart of Pharaoh will be turned, and his servants, against the people, and they will say, What this we did, that we sent forth Israel from serving us?

Proverbs 29:1

A Man of reproofs hardening the neck, shall be suddenly broken, and no healing.

Isaiah 26:10

Shall the unjust be shown favor? He learnt not justice; in the land of justice he will act perversely, and he will not see the majesty of Jehovah.

Jeremiah 34:7-11

And the strength of the king of Babel warred against Jerusalem, and against all the cities of Judah being left against Lachish, and against Azekah: for these remained of the cities of Judah, fortified cities.

Hosea 6:4

What shall I do to thee, O Ephraim? What shall I do to thee, O Judah? and your kindness as the cloud of the morning, and as the dew being early went away.

Zechariah 7:11-12

And they will refuse to attend, and they will give a stubborn shoulder, and their ears they made heavy from hearing.

Hebrews 3:8

Harden not your hearts, as in the exasperation, in the day of trial in the desert:

Hebrews 3:15

In that it is said, To day if ye will hear his voice, ye should not harden your hearts, as in the exasperation.

Revelation 16:9

And men were parched up with great heat, and they blasphemed the name of God, having power over these blows: and they repented not 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 will say to Moses, In thy going to turn back to Egypt, see all the wonders which I put in thy hand: do them before Pharaoh; and I will bind fast his heart and he shall not send forth the people.
Exodus 7:4
And Pharaoh will not hear to you; and I gave ray hand upon Egypt, and I brought forth my army, my people the sons of Israel, out of Egypt, with great judgments.
Proverbs 29:1
A Man of reproofs hardening the neck, shall be suddenly broken, and no healing.
Zechariah 7:11
And they will refuse to attend, and they will give a stubborn shoulder, and their ears they made heavy from hearing.
Hebrews 3:8
Harden not your hearts, as in the exasperation, in the day of trial in the desert:
Revelation 16:9
And men were parched up with great heat, and they blasphemed the name of God, having power over these blows: and they repented not to give him glory.

General references

Exodus 7:13
And Pharaoh's heart. will be strengthened, and he will not hear to them; as Jehovah said.
Exodus 8:32
And Pharaoh will make his heart heavy also in this time; he sent not forth the people.
Jeremiah 34:11
And they will turn back after this, and they will cause their servants and their maids to turn back whom they sent away free, and they subdued them for servants and for maids.