Job 41:24

His heart is as firm as a stone; yea, as hard as a piece of
the nether [millstone].
] Which must be understood not of the substance but of the qualities of it, being bold, courageous, undaunted, and unmerciful; which is true both of the whale and crocodile, and particularly of the crocodile: Aelianus ^F26 relates of one sort of them that they are unmerciful, though elsewhere ^F1, he represents them as fearful.