Job 39:8

He looks round on the mountains of his pasture. 64. The mountains of his pasture are the lofty contemplations of inward refreshment. For the more holy men abase themselves outwardly with contempt, the more abundantly are they supported within with the contemplation of revelations. Whence it is written; He hath disposed the ascents in his heart in the valley of tears; [Ps. 84, 6] because those, whom the valley of humility outwardly imprisons in tears, the ascent of contemplation elevates within. The mountains of pasture are also the lofty powers of angels: which therefore refresh us here by ministering and assisting, because they are fattened there with the inward dew of contemplation. And because, by the bounty of God, they protect us in every contest, they are well said to be beheld around. For we behold them present on all sides around us, by whose defence we are protected against our adversaries on every side. The mountains of pasture can be taken, still further, for the lofty sentences of Holy Scripture, of which it is said by the Psalmist; The high hills for the stags, [Ps. 104, 18] because those who know already how to make the leaps of contemplation, ascend the lofty summits of the Divine sentences, as the tops of mountains. And because the feeble cannot reach in truth to these tops, it is there rightly subjoined, the rock is a refuge for the urchins, because, namely, their understanding does not sublimely exercise the feeble, but faith alone in Christ humbly keeps them in. It follows; He searcheth after every green thing. 65. For parched in truth are all things, which, fashioned for a time, are dried up from the sweetness of the present life by the coming end, as if by the summer sun. But those are called green, which fade not away by any shortness of existence. […]

The other reason is because there he wanders more freely in search of pasture, and so he says, "He ranges the mountains for his pasture," since free access to different places to find his pasture lies open to him, and he receives the pastures themselves …

Commentary on Chapter XXXIX 4. Young ones - Notwithstanding their great weakness caused by their hard entrance into the world. Grow up - As with corn, that is, as if they were fed with corn.

The range of the mountains is his pasture,....

(2.) See how forward he is to engage: He goes on to meet the armed men, animated, not by the goodness of the cause, or the prospect of honour, but only by the sound of the trumpet, the thunder of the captains, and the shouting of the soldiers, which are as bellows to the fire of his innate courage, and make him spring forward with the utmost eagerness, as if he cried, Ha! ha!