Hebrews 3:8

harden not your hearts, as at Meriba and Massa in the desart:

Hebrews 3:15

which is imply'd by, "to-day since ye hear his voice, harden not your hearts, as at Meriba."

Revelation 16:9

and men were scorched with great heat, and blasphemed the name of God, who hath power over these plagues: 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

Hebrews 3:8
harden not your hearts, as at Meriba and Massa in the desart:
Revelation 16:9
and men were scorched with great heat, and blasphemed the name of God, who hath power over these plagues: and they repented not, to give him glory.