Hebrews 3:8

You must not harden your hearts as they did in provoking me, as on the day in the desert they tested me,

Hebrews 3:15

and yet the warning continues to be spoken: "If you but hear His voice, you must not harden your hearts as they did in provoking me."

Revelation 16:9

so that men were severely scorched, but they only cursed the name of God who had authority over these plagues, and would 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
You must not harden your hearts as they did in provoking me, as on the day in the desert they tested me,
Revelation 16:9
so that men were severely scorched, but they only cursed the name of God who had authority over these plagues, and would not repent and give Him glory.