Hebrews 3:8

do not harden your hearts as in the rebellion, on the day of testing in the wilderness,

Hebrews 3:15

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

Revelation 16:9

Men were scorched by the fierce heat, and they cursed the name of God who had power over these plagues, and they did not repent and 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

Hebrews 3:8
do not harden your hearts as in the rebellion, on the day of testing in the wilderness,
Revelation 16:9
Men were scorched by the fierce heat, and they cursed the name of God who had power over these plagues, and they did not repent and give him glory.