Everyone sins, and everyone knows it. While it is true that fallen human nature minimizes or redefines sin, everyone knows they don’t meet the standard of perfection. Whether they call them “sins” or “mistakes,” everyone will admit to having lied, lusted, or lashed out in anger at some point in their lives—if not regularly.
That being the case, what is the difference between the sins of believers and unbelievers? When a believer sins, is it the same as when an unbeliever sins?
The Nature of Sin
The two primary biblical definitions of sin are “missing the mark” (hamartia) and “without righteousness” (adikia). At its core, sin is a transgression of God’s law; it is to think and behave as if there were no law. The apostle John emphasizes that lawless characteristic when he writes, “Everyone who practices sin also practices lawlessness; and sin is lawlessness” (1 John 3:4).
John wrote his epistle to help believers test the authenticity of their faith (1 John 5:13). Unlike many today, John does not test saving faith on the basis of a signed card, a walk down the aisle, or even a prayer made in a moment of contrition. In the passage we’re considering in this series, he’s focused on the incompatibility of sin with saving faith, and he’s making three arguments for the holiness of believers.
John’s first argument is that sin is incompatible with the law of God. As we saw in 1 John 3:4, he explicitly equates sin with an attitude of lawlessness and rebellion against God (cf. Romans 8:7; Colossians 1:21).
Diagnosing Unbelievers’ Sin
John’s description of sin allows for no exceptions or double standards. Everyone who habitually practices sin is living in an ongoing condition of lawlessness. That’s not to say that they’re sinning to the full extent of their depravity. The lawlessness John refers to is more of an attitude than an action. It’s not merely transgressing God’s law—it’s living with an indifference to the law, as if there was no law-Giver at all.
We must not underestimate the severity of the unrepentant sin that flows from unbelief. We can’t define sin in bits and pieces as individual acts alone. Of course each individual sin is a serious offense to God, but we also need to be able to recognize and biblically diagnose the profound lawlessness of the unredeemed heart.
Diagnosing Believers’ Sin
If you’re a Christian, you no longer have that dominant attitude of lawlessness. The truly penitent heart resolves to obey God’s law (Psalm 19:7-11), deny fleshly lusts (Romans 13:14), resist the world’s allurements (Titus 2:12), and willingly submits to the sovereign Lordship of Jesus Christ in all things. Those whom God has saved and transformed have traded slavery to sin for slavery to God, as Paul wrote:
Do you not know that when you present yourselves to someone as slaves for obedience, you are slaves of the one whom you obey, either of sin resulting in death, or of obedience resulting in righteousness? But thanks be to God that though you were slaves of sin, you became obedient from the heart to that form of teaching to which you were committed, and having been freed from sin, you became slaves of righteousness. (Romans 6:16-18)
That’s not to say believers never sin—no honest Christian would make that claim. But when we do give in to temptation, we experience godly sorrow, not an attitude that is cavalier and rebellious. The believer’s sin is not the product of a heart bent in defiant lawlessness.
Instead we’re heartbroken over transgressing God’s law. It’s the attitude David displays in Psalm 32 and 51, where he pleads for God’s mercy in the aftermath of grievous sin. We share the frustration with lingering sin that Paul expresses in Romans:
For what I am doing, I do not understand; for I am not practising what I would like to do, but I am doing the very thing I hate. . . . For I know that nothing good dwells in me, that is, in my flesh; for the willing is present in me, but the doing of the good is not. For the good that I want, I do not do, but I practice the very evil that I do not want. But if I am doing the very thing I do not want, I am no longer the one doing it, but sin which dwells in me. (Romans 7:15, 18-20)
That penitent heartbreak comes from our love of God and His law. At salvation, each believer bows his knee to the lordship of Christ. It’s a commitment to obey Him, follow Him, and fulfil His law. The believer’s life is marked by wilful, loving submission to God’s law in the pursuit of holiness. We understand that the law isn't a system of works righteousness, or a legalistic set of outdated rules. It’s an expression of God’s holy character, and we join the refrain of Psalm 119, confessing “O how I love Your law! It is my meditation all the day” (Psalm 119:97).
Therefore, how could authentic believers live in open, unrepentant lawlessness? John says they can’t.
But the lawless nature of sin is only the first of three reasons John gives for his conclusion. Next time we’ll look at how sin is also incompatible with the work of Christ.
(Adapted from The MacArthur New Testament Commentary: 1-3 John.)