Job 41:27

He esteemeth iron as straw,.... You may as well cast a straw at him as a bar of iron; it will make no impression on his steeled back, which is as a coat of mail to him; so Eustathius affirms d that the sharpest iron is rebounded and blunted by him;

[and] brass as rotten wood; or steel, any instrument made of it, though ever so strong or piercing.

d Apud ibid. (Bochard. Hierozoic. par. 2. l. 5. c. 17. col. 785.)