Psalm 119 Verse 109. — My soul [life] is continually in my hand, etc. Why doth David say, "My soul is in mine hand"; had he called it out of the hand of God, and taken the care of it upon himself? Nothing less. His meaning is only this, — I walk in the midst of dangers and among a thousand deaths continually; I am in deaths often, my life is exposed to perils every day, yet do I not forget thy law: I keep close to thee, and will keep close to thee whatsoever comes of it. Augustine upon that place doth ingenuously confess that he understood not what David meant, by having his soul in his hands; but Jerome, another of the ancients, teaches us, that it is an Hebraism, signifying a state of most extreme peril. The Greeks also have drawn it into a proverb speaking the same thing.
But why doth the holding or putting the life in the hand signify the exposing of the life to peril? There is a twofold reason of it.
First. Because those things which are carried openly in the hand are apt to fall out of the hand, and being carried in sight, they are apt to be snatched or wrested out of the hand. And, therefore, though to be in the hand of God signifies safety, because his hand is armed with irresistible power to protect us; yet for a man to carry a thing in his own hand is to carry it in danger, because his hand is weak, and there are safer ways of carrying or conveying a thing than openly in the hand. If a man be to ride a long journey with any treasure about him, he doth not carry it in his hand, but puts it in some secret and close place where it may be hidden, and so be more secure. The Chaldee paraphrast [exegesist], to express the elegancy of that place forecited [cited previously] out of the Psalm, gives it thus, "My life is in as much danger as if it stood upon the very superficies [on the outside] or outside of my hand," as if he had no hold of it, but it stood barely upon his hand; for that which is set upon the palm of the hand, and not grasped, is in greater danger. Things safe kept are hidden or held fast.
Secondly. There is another reason of that speech, because when a man is about to deliver a thing or to give it up, he takes it in his hand. They that put themselves upon great perils and dangers for God and his people, deliver up their lives and their all to God. Hence that counsel of the Apostle (1 Peter 4:19): "Let them that suffer according to the will of God commit the keeping of their souls to him in well doing, as unto a faithful Creator." So here, the life of men in danger is said to be put in the hand, because such are, as it were, ready to deliver and commit their lives unto God, that he would take care of their lives to preserve them from the danger, or to take them to himself if they lose them in his service. — Joseph Caryl.From the additional notes to Charles Spurgeon's The Treasury of David.