Hard as a piece of the nether millstone. -- Old Testament -

Related:

• Canst thou draw out leviathan with an hook? -- Old Testament -
  Job xli,...
• He maketh the deep to boil like a pot. -- Old Testament -
  Job xli,...
• Blessed is he that considereth the poor. -- Old Testament -
  Psalm xli,...
• The eyes of a fool are in the ends of the earth. -
  Old Testament -- Proverbs xvii,...
• The king of terrors. -- Old Testament --
  Job xviii,...
• The land of the living. -- Old Testament --
  Job xxviii,...
• He that spareth his rod hateth his son. -- Old Testament -
  Proverbs xiii,...
• Clearer than the noonday. -- Old Testament --
  Job xi,...
• Fair weather cometh out of the north. -- Old Testament -
  Job xxxvii,...