Job 41:24
His heart will press as a stone; and it will press as the under millstone.
Isaiah 48:4
From my knowledge that thou wert hard, and thy neck an iron sinew, and thy forehead of brass:
Jeremiah 5:3
O Jehovah, are not thine eyes upon faithfulness? thou didst smite them, and they were not pained; thou didst consume them, they refused to take instruction: they made their faces firm above the rock; they refused to turn back.
Zechariah 7:12
And their heart they set a diamond from hearing the instruction and the words which Jehovah of armies sent by his spirit by the hand of the former prophets: and there will be great wrath from Jehovah of armies.