Jeremiah 17:9,10

The heart is deceitful above all things This passage, considered in connection with what precedes, may be understood in two points of view: 1st, As assigning a reason why we should not trust in man; namely, because he is not only weak and frail, and therefore may want power to help us in our necessities and distresses, but is also false and deceitful. Or, 2d, As giving us a caution to take care lest we deceive ourselves in supposing we trust in God when really we do not; this being a thing respecting which our own hearts are very apt to deceive us, as appears by this, that our hopes and fears are wont to rise or fall, according as second causes appear to be favourable or adverse. But it is true in the general, that there is greater wickedness in our hearts, by nature, than we ourselves are aware of, or suspect to be there. Nay, and it is a common mistake among mankind to think their own hearts a great deal better than they really are. The heart of man, in his corrupt and fallen state, is false and deceitful above all things; deceitful in its apprehensions of things, calling evil good and good evil, putting false colours upon things, crying peace to those to whom peace does not belong, and cheating men to their own ruin; deceitful in the hopes and promises which it excites and nourishes, and in the assurances which it gives. And desperately wicked Hebrews ואנשׁ הוא, literally, and desperate, or, as Blaney renders it, it is even past all hope; who can know it? That is, “humanly speaking, there is no possibility that any one should trace it through all its windings, and discover what is at the bottom of it.” In short, it is unsearchable by others, deceitful with reference to ourselves, and abominably wicked; so that neither can a man know his own heart, nor can any one know that of his neighbour. I the Lord search the heart I am perfectly acquainted with it, and with all the wickedness that lodges in it: all its thoughts, counsels, and designs, however secret; all its intentions, affections, and determinations lie open to my inspection: and my piercing eye penetrates into its inmost recesses. I try the reins To pass a true judgment on what I discern, and to give every thing therein its true character and due weight. I try the heart, as the gold is tried, whether it be standard weight or not; or, as the prisoner is tried, whether he be guilty or not. And this judgment, which I make of the hearts, is in order to my passing a true judgment upon the man, even to give to every man according to his ways According to the desert and tendency of them; life to those that have walked in the ways of life, and death to those that have persisted in the paths of the destroyer; and according to the fruit of his doings The effect and influence which his doings have had on others; or according to what is determined by the word of God to be the fruit of men's doings, blessings to the obedient, and curses to the disobedient.