David here lays down this great doctrine, That the God with whom we have to do has a perfect knowledge of us, and that all the motions and actions both of our inward and of our outward man are naked and open before him.

I.He lays down this doctrine in the way of an address to God; he says it to him, acknowledging it to him, and giving him the glory of it. Divine truths look fully as well when they are prayed over as when they are preached over, and much better than when they are disputed over. When we speak of God to him himself we shall find ourselves concerned to speak with the utmost degree both of sincerity and reverence, which will be likely to make the impressions the deeper.

II.He lays it down in a way of application to himself, not, "Thou hast known all," but, "Thou hast known me; that is it which I am most concerned to believe and which it will be most profitable for me to consider." Then we know these things for our good when we know them for ourselves, Job 5:27. When we acknowledge, "Lord, all souls are thine," we must add, "My soul is thine; thou that hatest all sin hatest my sin; thou that art good to all, good to Israel, art good to me." So here, "Thou hast searched me, and known me; known me as thoroughly as we know that which we have most diligently and exactly searched into." David was a king, and the hearts of kings are unsearchable to their subjects (Pro 25:3), but they are not so to their Sovereign.

III.He descends to particulars: "Thou knowest me wherever I am and whatever I am doing, me and all that belongs to me." 1. "Thou knowest me and all my motions, my down-sitting to rest, my up-rising to work, with what temper of mind I compose myself when I sit down and stir up myself when I rise up, what my soul reposes itself in as its stay and support, what it aims at and reaches towards as its felicity and end. Thou knowest me when I come home, how I walk before my house, and when I go abroad, on what errands I go." 2. "Thou knowest all my imaginations. Nothing is more close and quick than thought; it is always unknown to others; it is often unobserved by ourselves, and yet thou understandest my thought afar off. Though my thoughts be ever so foreign and distant from one another, thou understandest the chain of them, and canst make out their connexion, when so many of them slip my notice that I myself cannot." Or, "Thou understandest them afar off, even before I think them, and long after I have thought them and have myself forgotten them." Or, "Thou understandest them from afar; from the height of heaven thou seest into the depths of the heart," Psa 33:14. 3. "Thou knowest me and all my designs and undertakings; thou compassest every particular path; thou siftest (or winnowest) my path" (so some), "so as thoroughly to distinguish between the good and evil of what I do," as by sifting we separate between the corn and the chaff. All our actions are ventilated by the judgment of God, Psa 17:3. God takes notice of every step we take, every right step and every by-step. He is acquainted with all our ways, intimately acquainted with them; he knows what rule we walk by, what end we walk towards, what company we walk with. 4. "Thou knowest me in all my retirements; thou knowest my lying down; when I am withdrawn from all company, and am reflecting upon what has passed all day and composing myself to rest, thou knowest what I have in my heart and with what thought I go to bed." 5. "Thou knowest me, and all I say (Psa 139:4): There is not a word in my tongue, not a vain word, nor a good word, but thou knowest it altogether, knowest what it meant, from what thought it came, and with what design it was uttered. There is not a word at my tongue's end, ready to be spoken, yet checked and kept in, but thou knowest it." When there is not a word in my tongue, O Lord! thou knowest all (so some read it); for thoughts are words to God. 6. "Thou knowest me in every part of me: Thou hast beset me behind and before, so that, go which way I will, I am under thy eye and cannot possibly escape it. Thou hast laid thy hand upon me, and I cannot run away from thee." Wherever we are we are under the eye and hand of God. perhaps it is an allusion to the physician's laying his hand upon his patient to feel how his pulse beats or what temper he is in. God knows us as we know not only what we see, but what we feel and have our hands upon. All his saints are in his hand.

IV.He speaks of it with admiration (Psa 139:6): It is too wonderful for me; it is high. 1. "Thou hast such a knowledge of me as I have not of myself, nor can have. I cannot take notice of all my own thoughts, nor make such a judgment of myself as thou makest of me."? 2. "It is such a knowledge as I cannot comprehend, much less describe. That thou knowest all things I am sure, but how I cannot tell." We cannot by searching find out how God searches and finds out us; nor do we know how we are known.

Such knowledge is too wonderful for me,.... Meaning either the knowledge of himself, such as God had of him, which was vastly superior to what he had of himself; and especially the knowledge of other persons and things, whether visible or invisible, in heaven, earth, or hell; things past, present, and to come; or else the manner in which God knew all this was amazing to him, and quite impenetrable by him; that he did know him, his thoughts, his words and actions, and so those of all others, was easy of belief; but how he should know all this was past his conception, and struck him with the profoundest admiration;

it is high; sublime, out of his reach, beyond his comprehension;

I cannot attain unto it; neither to such knowledge, nor to comprehend what it is in God; and how he should have it, and in what manner he exercises it. Kimchi, Jarchi, and Aben Ezra, connect the words with the following, as if the matter of his wonder and astonishment was the omnipresence of God, or where he should find a place to flee from him.