Job 40:20 - Joseph Benson’s Commentary on the Old and New Testaments

The mountains bring him forth food Though this creature be so vastly large, and require much food, and no man careth for it, yet God provides for it out of his own stores, and makes the desert mountains to afford it sufficient sustenance. This particular of the description seems more applicable to the elephant than the hippopotamus, which, though he fetches his food, in a great measure, from the land, feeding on the herbage on the banks of the Nile, and among the lakes and fens of Ethiopia, through which that river passes, yet can hardly be said to pasture upon the mountains. Both animals consume great quantities of food, and it must be acknowledged to be an instance of the goodness of God that he hath so ordered it that they feed on grass, and the other products of the field, and not on flesh; for if the latter had been their usual food, great multitudes of creatures must have died continually to keep them alive. Where all the beasts of the field play This is equally applicable both to the elephant and the river-horse. The beasts of the field not only feed securely, but sport themselves by both of them, being taught by experience that they are gentle and harmless, and never prey upon them.