Job 41:24

His heart is as firm as a stone, Yea, firm as the nether millstone.

Isaiah 48:4

Because I knew that thou are obstinate, and thy neck is an iron sinew, and thy brow brass,

Jeremiah 5:3

O LORD, do not thine eyes look upon truth? Thou have stricken them, but they were not grieved. Thou have consumed them, but they have refused to receive correction. They have made their faces harder than a rock. They have refused t

Zechariah 7:12

Yea, they made their hearts as an adamant stone, lest they should hear the law, and the words which LORD of hosts had sent by his Spirit by the former prophets. Therefore great wrath came from LORD of hosts.

Treasury of Scripture Knowledge

Summary

His heart is as firm as a stone; yea, as hard as a piece of the nether millstone.

Bible References

As hard

Isaiah 48:4
Because I knew that thou are obstinate, and thy neck is an iron sinew, and thy brow brass,
Jeremiah 5:3
O LORD, do not thine eyes look upon truth? Thou have stricken them, but they were not grieved. Thou have consumed them, but they have refused to receive correction. They have made their faces harder than a rock. They have refused t
Zechariah 7:12
Yea, they made their hearts as an adamant stone, lest they should hear the law, and the words which LORD of hosts had sent by his Spirit by the former prophets. Therefore great wrath came from LORD of hosts.