Surely the mountains bring him forth food. Neither the hippopotamus nor the elephant is an inhabitant of "mountains,'' according to our use of the word. But the harim ( הָרִים) of the original is used of very moderate eminences.
In the highly poetical language of Job, and especially of this passage, the term may well be applied to the hills on either side of the Nile, which approach closely to the river, and to this day furnish the hippopotamus with a portion of its food.
Where all the beasts of the field play. By "the beasts of the field" seem to be meant the cattle and other do-mastic animals which are not driven from their pasture-grounds by the "river-horse".