The answer is the distinction between law and gospel. To quote an article in the Lutheran Study Bible, “One of the principles of Law and Gospel is that the Law is used with unrepentant sinners and the Gospel is used with repentant sinners.” Or, to use the words of Martin Luther, “For this also must be noted: that as the voice of the law is brought to bear only upon those who neither feel nor know their sins…so the word of grace [i.e., the gospel] comes only to those who are distressed by a sense of sin and tempted to despair” (Bondage of the Will).
The law’s purpose is to awaken a dead—or, at least, a hard—conscience; the gospel’s purpose is to soothe a convicted conscience. The Pharisees often displayed the former, whereas the more blatant sinners often demonstrated the latter.
In order to wrap some meat of practicality around these bones of theory, let’s look at three different examples from Scripture.
When the rich young ruler asks Jesus what a person needs to do to inherit eternal life, Jesus answers by listing several commandments. The ruler confidently—and mistakenly—states that he has kept all of them from his youth. Such obedience, however, is impossible. Instead of arguing with the ruler, though, Jesus ups the ante: “One thing you lack: Go your way, sell whatever you have and give to the poor, and you will have treasure in heaven; and come, take up the cross, and follow Me” (v. 21).
Jesus is still speaking with the voice of the law. The young man’s misguided notion of his own goodness means he is not ready to hear the gospel. The law still hasn’t done its work; indeed, the man has misinterpreted God’s standard as being attainable. Thus, Jesus zeroes in on the root of the man’s problem (the idolatry of his wealth) with a proclamation of the law. Christ is showing this young man, who thinks he is near salvation, just how far from salvation he actually is.
Law and Gospel
In 2 Samuel 12, the prophet Nathan approaches King David with a story of a rich man who violently mistreats his neighbor. When David expresses anger over the misdeed, Nathan reveals that the criminal is actually David himself. He then rehearses how David has specifically broken God’s law, adding that there will be future repercussions of these sins, including that members of his own family would rise up against him (v. 11).
With the light of the law shining down on his now exposed sin, David’s hardened conscience is softened. In sorrow, he confesses the evil of his transgression. Nathan responds by speaking with the voice of the gospel: “The LORD also has put away your sin; you shall not die” (v. 13). This gospel promise strengthens David’s heart, giving him hope even when he later faces the consequences Nathan prophesied. (Read Psalm 3 as an example, where David proclaims confidence in God’s favor, even while experiencing the Lord’s discipline.)
We find a beautiful gospel promise in Ezekiel 33:
“As I live,” says the Lord GOD, “I have no pleasure in the death of the wicked, but that the wicked turn from his way and live. Turn, turn from your evil ways! For why should you die, O house of Israel?” (v. 11)
These words have often been mistaken as a statement of law, where God is pleading with hardened sinners in an attempt to win them over. In reality, this verse is a cry of the gospel, aimed at sinners whose consciences have already been pierced. Luther says about this passage,
None receive it with joy and gratitude but those who are distressed and troubled at death, those in whom the law has already completed its work, that is, given knowledge of sin [Rom. 3:20]. Those that have not yet experienced the work of the law, who do not recognize their sin and have no sense of death, scorn the mercy promised by [this] word.
Depending on the circumstance, the law or the gospel—or both—may be necessary to sway a sinner’s heart. To be clear, we all need to hear both eventually, but the self-righteous often require a healthy dose of the law, whereas delinquents with guilty consciences often need a healthy dose of the gospel. Whatever the case, it takes great wisdom to use the law and gospel rightly. Thanks be to God, the master craftsman, who can teach us how to use these tools well!