Job 41:24

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

Job 41:24 In-Context

22 In his neck remaineth strength, and sorrow is turned into joy before him.
23 The flakes of his flesh are joined together: they are firm in themselves; they cannot be moved.
24 His heart is as firm as a stone; yea, as hard as a piece of the nether millstone.
25 When he raiseth up himself, the mighty are afraid: by reason of breakings they purify themselves.
26 The sword of him that layeth at him cannot hold: the spear, the dart, nor the habergeon.
The King James Version is in the public domain.