Job 41:24
His heart is as strong as stone, it is as hard as a lower millstone.
Isaiah 48:4
Because I knew that you are obstinate, and because your neck is an iron sinew, and your forehead is bronze,
Jeremiah 5:3
LORD, don't your eyes look for truth? You struck them, but they didn't flinch. You brought them to an end, but they refused to receive discipline. They made their faces harder than stone, and they refused to repent.
Zechariah 7:12
They made their hearts hard like a diamond, to keep from obeying the Law and the messages that the LORD of the Heavenly Armies sent by his Spirit through the former prophets.
Treasury of Scripture Knowledge
Summary
His heart is as firm as a stone; yea, as hard as a piece of the nether millstone.
As hard
Bible References
As hard
Isaiah 48:4
Because I knew that you are obstinate, and because your neck is an iron sinew, and your forehead is bronze,
Jeremiah 5:3
LORD, don't your eyes look for truth? You struck them, but they didn't flinch. You brought them to an end, but they refused to receive discipline. They made their faces harder than stone, and they refused to repent.
Zechariah 7:12
They made their hearts hard like a diamond, to keep from obeying the Law and the messages that the LORD of the Heavenly Armies sent by his Spirit through the former prophets.