He cutteth out rivers among the rocks - That is, in his operations of mining, he cuts channels for the water to flow off through the rocks. This was done, as it is now, for the purpose of drawing off the water that accumulates in mines.
His eye seeth every precious thing - Every valuable mineral or precious stone that lies imbedded in the rocks. It is evident from this, that mining operations were carried to a considerable extent in the time of Job. The art of thus penetrating the earth, and laying open its secret treasures, indicate an advanced stage of society - a stage much removed from barbarism.

He cutteth out rivers among the rocks - He cuts canals, adits, etc., in the rocks, and drives levels under ground, in order to discover loads or veins of ore. These are often continued a great way under ground; and may be poetically compared to rivers, channels, or canals.
His eye seeth every precious thing - He sinks those shafts, and drives those levels, in order to discover where the precious minerals lie, of which he is in pursuit.

He cutteth out rivers among the rocks,.... By cleaving rocks asunder in order to find out things of value in the cliffs of them; or by cutting his way through them, the miner opens a course for rivers and floods of water, to drain off from his mines, and so can go on with his works more comfortably, and with success; though sometimes they sink through high rocks, till they go so far below their basis, that they can go no further for water, in some places forty or fifty fathom deep (i):
and his eye seeth every precious thing; in the cliffs of the rock, or at the bottom of the rivers and floods, as they go off, or in the mines he digs, even gold or silver, or precious stones: hence came the fable of Lynceus, and from him the phrase of Lyncean eyes (k), who was said to see all things under the earth, because he was the first that searched for metals, as brass, silver, &c. and in search of them carried lamps, or links, under the earth (l). This verse is also by some ascribed to God, who is said to cleave the fountain and the flood, and to dry up mighty rivers; and also to open rivers in high places, in hills, mountains, and rocks, as well as sometimes in the middle of the valleys, Psalm 74:15; and who, in a spiritual sense, has cut out and opened the river of his pure love and grace, which flows from the throne of God and the Lamb; and the fulness of grace in Christ, which is as rivers of water in a dry land; and the graces of the Spirit in his people, which flow out of them as rivers of living water; and his word and ordinances in his church, which are the rivers of pleasure he makes his saints to drink of in it: and his eye of omniscience, which sees all things in particular, sees all the precious things in nature; the precious things of heaven, and earth, and sea; the precious things brought forth by the sun and moon; and the precious tidings of the ancient mountains and everlasting hills, the gold, silver, and precious stones that lie hid in the bowels of them, Deuteronomy 33:13; and who also sees all precious persons, and things, in a spiritual sense; he beholds his precious Son, his precious blood, righteousness, and sacrifice, with delight and pleasure; and his eye of love, grace, and mercy, upon the precious sons of Zion, comparable to fine gold, jewels, and precious stones; and sees all the precious graces of the Spirit in them, with acceptance and good will.
(i) Philos. Transaet. abridged, vol. 2. p. 469. (k) Horat. Sermon. l. 1. Satyr. 2. v. 90. (l) Palaephat. de Incredib. c. 10.

He cuts channels to drain off the waters, which hinder his mining; and when the waters are gone, he he is able to see the precious things in the earth.

Seeth - Even those which no human art or industry was ever able to discover.