We do it when we trust Him for the salvation of our souls. There are a great many good Christian people who go mourning all their days, or, at least, sometimes mourning and sometimes indifferent. The most that they venture to say is, 'But I cannot be sure.' Our grandfathers used to sing:--
''Tis a point I long to know, Oft it causes anxious thought.'
Why should it cause anxious thought? Take your own personal salvation for granted, and work from that. Do not work _towards_ it. If you have gone to Christ and said, 'Lord, I cannot save myself; save me. I am willing to be saved,' be sure that you have the salvation that you ask, and that if you have put your soul in that fashion into God's hands, any incredible thing is credible, and any impossible thing is possible, rather than that you should fail of the salvation which, in the bottom of your hearts, you desire. Take the burden off your backs and put it on His. Do not be for ever questioning yourselves, 'Am I a saved man?' You will get sick of that soon, and you will be very apt to give up all thought about the matter at all. But take your stand on the fact, and with emancipated and buoyant hearts, and grateful ones, work from it, and because of it. And when sin rises up in your soul, and you say to yourselves, 'If I were a Christian I could not have done that,' or, 'If I were a Christian I could not be so-and-so'; remember that all sin is inconsistent with being a Christian, but no sin is incompatible with it; and that after all the consciousness of shortcomings and failure, we have just to come back to the old point, and throw ourselves on God's love. His arms are open to clasp us round. 'Into Thy hands I commit my spirit.'
Further, the Psalmist meant, by committing himself to God, trusting Him in reference to daily life, and all its difficulties and duties. Our act of trust is to run through everything that we undertake and everything that we have to fight with. Self-will wrenches our souls out of God's hands. A man who sends his securities to the banker can get them back when he likes. And if we undertake to manage our own affairs, or fling ourselves into our work without recognition of our dependence upon Him, or if we choose our work without seeking to know what His will is, that is recalling our deposit. Then you _will_ get it back again, because God does not keep anybody's securities against his will--you will get it back again, and much good it will do you when you have got it! Self-will, self-reliance, self-determination--these are the opposites of committing the keeping of our souls to God. And, as I say, if you withdraw the deposit, you take all the burden and trouble of it on your own shoulders again. Do not fancy that you are 'living lives of faith in the Son of God,' if you are not looking to Him to settle what you are to do. You cannot expect that He will watch over you, if you do not ask Him where you are to go.
But now there is another thing that I would suggest, this committing of ourselves to God which begins with the initial act of trust in Him for the salvation of our souls, and is continued throughout life by the continual surrender of ourselves to Him, is to be accompanied with corresponding work. The Apostle Peter's memory is evidently hovering round this verse, whether he is consciously quoting it or not, when he says, 'Let them that suffer according to the will of God commit the keeping of their souls to Him _in welldoing_,' which has to go along with the act of trust and dependence. There must come the continual ordering of the life in accordance with His will; for 'well-doing' does not mean merely some works of beneficence and 'charity,' of the sort that have monopolised to themselves the name in latter days, but it means the whole of righteous conduct in accordance with the will of God.