Behold, he is in thine hand - He is at thy disposal; see Job 1:12, Margin.
But save his life - Margin, "only." This was to be the only limitation. It would seem that he had the power to make any selection of disease, and to afflict him in any manner, provided it did not terminate fatally. The keen sorrows which Job afterward endured showed the malignancy of the tempter; evinced his ingenuity in inflicting pain, and his knowledge of what thc human frame could be made to bear.

But save his life - His body thou shalt have permission to afflict, but against his life thou shalt have no power; therefore take care of his life. The original, נפשו שמר naphsho shemor, may be translated, keep his soul; but the word also signifies life; yet in the hands of the destroyer the life of this holy man is placed! How astonishing is the economy of salvation! It is so managed, by the unlimited power and skill of God, that the grand adversary of souls becomes himself, by the order of God, the preserver of that which the evil of his nature incessantly prompts him to destroy!

And the LORD said unto Satan, Behold, he [is] in thine hand; but save (g) his life.
(g) Thus Satan can go no further in punishing than God has limited him.

And the Lord said unto Satan, behold, he is in thine hand,.... Well may a behold be prefixed to this, it being matter of wonder and astonishment that a saint and servant of God should be permitted to be in the hand of Satan; which yet must not be so understood; as if he was off of, and no more upon the heart of God; or as if he was out of the hands of God, and out of the hands of Christ; or as if he was become Satan's property, and a child of his; for neither of these can be true of a good man: nothing can separate him from the love of God; not Satan and all his principalities and powers; nor can men or devils pluck them out of his hands, nor out of the hands of his son; nor can those who are the children of God be any more the servants of sin, or the vassals of Satan; or in other words, nor can any of them be a child of God one day, and a child of the devil the next, which is the divinity of some men: nor is the sense of this passage, that Satan had leave to do with Job as he pleased, for then he would have utterly destroyed him; but the power granted him was a limited one, as follows:
but save his life: or "soul" (y); which some understand of his rational soul, that which remains after death, and which, Maimonides (z) observes, Satan has no power over; and according to some the meaning is, do not disturb his mind to distraction, so as to deprive him of his senses, and of the exercise of his rational powers, which through the influence of Satan men have sometimes lost; see Mark 5:4; this is barred against in the permission granted; for otherwise it would not have been a proper trial of Job's integrity; for, should he have been deprived of his reason, and uttered ever such bad things, it would have been no proof of his insincerity; as may be observed in good men in a delirium, they will utter bad words, and do or attempt to do bad things, which is not to be ascribed to their want of grace, but to their want of reason: but rather "life" is meant; not Job's spiritual life, for that was in no danger of being lost; all the devils in hell cannot deprive a truly good man of his spiritual life; grace in him is a well of living water, springing: up to eternal life; he can never die the second death; his life is hid with Christ in God, and is bound up in the bundle of life with the Lord his God, who so is out of the reach of Satan; but corporeal life, which the devil by permission may take away, and is said to have the power of death, which by leave he exercised over men, but here he is restrained from it: Job's life must be spared, that it might fully appear he got the victory over Satan, and stood in his integrity; and that he might still glorify God in a course of afflictions he was yet to endure, in the exercise of his faith, hope, love, patience, humility, submission, and resignation of his will to God; and besides, his appointed time was not come, he had many more days, months, and years, the number of which were with God, to live in the world, as he accordingly did.
(y) "animum ejus", Pagninus, Montanus, Cocccius, Schmidt, Schultens. (z) Moreh Nevochim, par. 3. c. 22. p. 398.

but save--rather, "only spare his life." Satan shows his ingenuity in inflicting pain, and also his knowledge of what man's body can bear without vital injury.

The Grant of New Power:
6 And Jehovah said to Satan, Behold, he is in thy hand; only take care of his life.
Job has not forfeited his life; permission is given to place it in extreme peril, and nothing more, in order to see whether or not, in the face of death, he will deny the God who has decreed such heavy affliction for him. נפשׁ does not signify the same as חיּים; it is the soul producing the spirit-life of man. We must, however, translate "life," because we do not use "soul" in the sense of ψυχή, anima.

In thine hand - If God did not chain up the roaring lion, how soon would he devour us! As far as he permits the wrath of Satan and wicked men, to proceed against his people, he will make it turn to his praise and theirs, and the remainder thereof he will restrain. Job, in being thus maligned of Satan, was a type of Christ. He had permission to bruise his heel, to touch his bone and his flesh; yea, and his life also; because by dying he was to do what Job could not do, to destroy him that had the power of death.