job 40:15 Behold now behemoth, which I made with thee; he eateth grass as an ox. - Free Bible Online

      15-24. God shows that if Job cannot bring under control the lower animals (of which he selects the two most striking, behemoth on land, leviathan in the water), much less is he capable of governing the world.
      behemoth--The description in part agrees with the hippopotamus, in part with the elephant, but exactly in all details with neither. It is rather a poetical personification of the great Pachydermata, or Herbivora (so "he eateth grass"), the idea of the hippopotamus being predominant. In Job 40:17, "the tail like a cedar," hardly applies to the latter (so also Job 40:20, 23, "Jordan," a river which elephants alone could reach, but see on Job 40:23). On the other hand, Job 40:21, 22 are characteristic of the amphibious river horse. So leviathan (the twisting animal), Job 41:1, is a generalized term for cetacea, pythons, saurians of the neighboring seas and rivers, including the crocodile, which is the most prominent, and is often associated with the river horse by old writers. "Behemoth" seems to be the Egyptian Pehemout, "water-ox," Hebraized, so-called as being like an ox, whence the Italian bombarino.
      with thee--as I made thyself. Yet how great the difference! The manifold wisdom and power of God!
      he eateth grass--marvellous in an animal living so much in the water; also strange, that such a monster should not be carnivorous.

JFB.