The heart is deceitful above all things, and incurable; who can know it?
Jeremiah has just set two men side by side: one leans on human strength and dries up like desert scrub, the other trusts the Lord and stays green in a drought. Here is why the first choice comes so naturally to us — and the verdict raises two questions: how bad is the heart, and if no one can know it, who can?
Most people admit that some human beings do terrible things. Few of them include themselves. One writer presses the question of who exactly the prophet has in view:
Many people say that only the worst examples of fallen humanity commit the disgusting sins Scripture forbids, and that the rest of us do not. This is a complete mistake. Hear what the Holy Spirit says in the seventeenth chapter of the prophet Jeremiah. "The heart is deceitful above all things, and desperately wicked." Whose heart is he speaking of? Is it the heart of some terrible criminal, or of someone who has never been taught? No; it is the human heart, the heart of the writer and of the reader of these lines.
This is not a conclusion anyone reaches by looking inward. It is a judgment handed down, and one that our own sense of ourselves keeps disputing:
The teaching that the heart is desperately wicked applies to everyone. It is the verdict of the God who knows all things, however much our own experience questions it. Every believer in the Lord Jesus Christ has doubted it about himself, until God Himself taught it to him... Receiving this doctrine in its power helps to keep the believer humble and watchful.
The ESV reads "desperately sick" here. Older versions read "desperately wicked," and one writer compares those versions and defends the stronger wording:
"Desperately wicked" clearly renders the Hebrew word well when that word describes moral evil rather than physical sickness. "Incurable" might suit this verse, but it would not do in other passages... The old Latin version, the Vulgate, is far worse... it gives a much weaker reading, if not a false one.
Later in the chapter, God's dealings with Israel expose that same incurable heart:
The human heart is incurable, and so deceitful that no child of Adam can see how corrupt it is (v. 9). It is set on doing evil and on leaving God, however many privileges it is given. In the Old Testament the Lord tested man, and He tested Israel, His chosen nation, under the law — but only to show how completely ruined man is (v. 10).
The question at the end of the verse is not rhetorical decoration. It marks the limit of self-examination, and one writer confesses that limit about himself:
If I examine my own heart I cannot find it out. I know more of God's heart than I do of my own. My own is so slippery that I cannot get to the bottom of it, for "the heart is deceitful above all things, and desperately wicked: who can know it?" The best man on earth will be the first to admit this.
Jeremiah answers his own question in the next breath, and one writer finds comfort in that answer:
We do not know how deceitful our own hearts are, for the same passage that tells us it is deceitful above all things and desperately wicked goes on to ask, "Who can know it?" The prophet answers at once: "I the Lord search the heart and test the mind" (Jer. 17:10). The One who searches and knows is the One who alone is able to keep us from falling, and to restore us when we fall.
That searching gaze has not made God withdraw. Commenting on the same verses, another writer notes what God does with what He sees: "He has sounded its depths... So He knew and knows what we are, yet in sovereign love and grace He has loved us and bears with His own." — Arno Clemens Gaebelein
If the verse is true, then consulting your own heart as a guide is a poor plan. One writer puts the reasoning simply (older versions read "his own heart" here; the ESV reads "his own mind"):
"Whoever trusts in his own heart is a fool." Why? Because the heart "is desperately wicked" and "deceitful above all things." Only a fool would trust a wicked man, or believe someone who lies through and through.
A disease called incurable rules out treatment and calls for something else entirely:
By nature our hearts are like a rotten egg: so bad they could not be worse, and so bad that nothing can make them better. When we learn that, we see the truth of the word, "You must be born again." Then we give up trying to improve ourselves, and cast ourselves wholly on the Lord.
- The heart diagnosed. The verse describes not criminals but "the heart of the writer and of the reader" — everyone's.
- The heart doubted. Every believer doubts this about himself until God teaches it. Accepting it keeps him humble and watchful.
- The heart unfathomable. No child of Adam can reach the bottom of it. The honest man admits he knows God's heart better than his own.
- The heart searched. The Lord answers "Who can know it?" at once: He does. And the One who knows is the One able to keep us and restore us.
- The heart replaced. Because it is incurable, it cannot be repaired — it must be made new. Give up self-improvement and cast yourself wholly on the Lord.
I Jehovah search the heart, I try the reins, even to give each one according to his ways, according to the fruit of his doings.
The verse before this one calls the human heart deceitful beyond anyone's understanding. This verse is God's reply: He searches that heart Himself, and He repays each person for the way they have lived.
God's answer does more than expose the heart:
We do not know how deceitful our own hearts are. The same passage that tells us the heart is deceitful above all things and desperately wicked goes on to ask, "Who can know it?" At once the prophet gives the answer: "I the Lord search the heart, I try the reins." The One who searches and knows is the only One able to keep us from falling, and to restore us when we fall.
Where the ESV says God tests "the mind," older translations say He tries "the reins." That word is not about control or restraint. It names a part of the body:
The kidneys, used symbolically for the inward thoughts and feelings.
So God's search covers the whole inner person: the heart, and the thoughts and feelings hidden under it.
No one but God can search hearts. One writer notes that what God declared about Himself here is later declared about Jesus:
This was full, complete, perfect understanding of man, in the way God understands. Jesus was God in His knowledge of man. What the Lord declared Himself to be through His prophet, Jesus is now declared to be by the Gospel writer. Jesus did not know fallen man, or the heart's corruption, by sympathy. He knew it all as God — the One who searches the hearts and tries the reins of the children of men, to give every man according to his ways.
Another writer applies it to Christ and the churches:
In Old Testament times this belonged to the Lord alone (Jer. 17:10). The churches are to learn the lesson — or rather to know that Christ, the One they have to deal with, carries out this solemn work. He knows everything.
The verse states the purpose of the search: to repay each person according to their ways and the fruit of their deeds. One writer shows what that testing proved about Israel:
The heart of man cannot be cured. It is set on doing evil and departing from God, however greatly privileged it may be. The Lord was testing man in the Old Testament, testing favoured Israel under law, but only to prove his utter ruin (v. 10). Judgment must therefore fall. For believers now it has already taken place at the cross of our Lord Jesus Christ.
One writer marks a change. Under law, God searched the heart to reward each person's work. In Romans He searches it with a different aim:
By the apostle, God is revealed as the Searcher of the heart with another intent. "He who searches hearts knows what is the mind of the Spirit." He is not searching the heart to reward the works, or even to refine as gold is refined. In His search of the heart He finds the exercises of the spirit. This is what He looks at there. It is not a search ending in the detection of evil, but of good — good to be owned according to Himself, not evil to be judged and punished. (Rom. 8:27.)
This truth works two ways. First, it guards a person against self-confidence:
Receiving this teaching with real power helps to keep the believer humble and watchful. So "the Lord keeps the feet of His saints," putting His fear in their hearts. They live in the fear of the Lord all day long. So they are kept from many an outbreak of desperate wickedness, the usual result of walking in self-confidence.
Second, it becomes a comfort — once you know what the Searcher is like:
Has it ever been a comfort to you that Christ searches the heart and the reins? That there is not one single thing God does not see? … Whatever comes out, it is the greatest comfort to know that He knew what was inside before. What comes out must have been inside first. You cannot bear God's searchings until you know that He is love.
- Searched. No one can know the human heart. God searches it, and He tests the inward thoughts and feelings.
- Divine. Searching hearts belongs to God alone. So Jesus's knowledge of man, and Christ's searching of the churches, are claims to be God.
- Repaid. The searching ends in repayment. Each person receives according to his ways and the fruit of his deeds.
- Redirected. Under law the search proved man's ruin. For the believer, judgment fell at the cross. God now searches the heart to find the mind of the Spirit there.
- Rested. This truth humbles self-confidence and keeps the believer watchful. And since the One who sees everything is love, His searching becomes comfort, not terror.