This study is based upon the New City Catechism.
Everyone who makes a practice of sinning also practices lawlessness; sin is lawlessness. (1 John 3:4)
“Sin” is a term we easily regulate to an abstraction. Sin is a spiritual rash or an invisible demon. Sin is something we all have, but it doesn’t really look like anything. Categorizing sin as an abstraction is the vessel of many vices. We can harbor evil within our bodies easily when we think of sin simply as a foreign enemy of the mind. We need to do away with the abstractions. Therefore, consider the following three characteristics of sin.
First, sin is breaking God’s law. “Everyone who makes a practice of sinning also practices lawlessness; sin is lawlessness” (1 John 3:4). Sin is not subjective: we don’t get to decide what is or isn’t sin. God has revealed His law to us, and His law is the yardstick by which we measure sin. Therefore, sin is a revelatory matter. Sin is not defined by the imagination, it is defined by God’s revelation. Sin is objective. In God’s creation, it is not relative. This means we do not judge whether something is sinful or how sinful it is, in relation to other created things. Your neighbor is not the standard of righteousness by which you are judged. God’s law is the standard.
Further, if sin is the breaking of God’s law, then you don’t have the right to call something sinful that does not break God’s law. The definition works both ways. We often place unnecessary burdens on ourselves and others, when we call matters sinful which God does not. This is the danger of moralism, and it is an affront to God’s law and revelation.Christians should not try to be holier than God. If He has not identified something as sinful, then neither should we.
Second, sin is tangible. Sin is a spiritual issue, but is by no means regulated to the invisible realm. Sin is just as practical and specific as God’s law, and God’s law addresses every matter (2 Timothy 3:16-17). You can smell sin. You can taste sin. It has weight, it takes up space, and your eyes can see it. You can hold sin in your hand and when it speaks, you can hear it. This means that a preacher who only preaches against abstract wickedness is not really preaching against sin. A mother who only warns her child against invisible evil is not issuing a very helpful warning. God’s deals with tangibles, and therefore sin deals with tangibles. Righteousness looks like something, and therefore unrighteousness also looks like something.
Third, sin is a grave matter. John’s ambition in 1 John 3:4 was to make plain the seriousness of sin. The highest dishonor a man can ever commit is to disobey God. Sinners do not understand this, because they constantly grow callous and unresponsive in sin. “They have become callous and have given themselves up to sensuality, greedy to practice every kind of impurity” (Ephesians 4:19). Let the testimony of Moses teach you how man should posture himself before God:
The Lord passed before him and proclaimed, “The Lord, the Lord, a God merciful and gracious, slow to anger, and abounding in steadfast love and faithfulness, keeping steadfast love for thousands, forgiving iniquity and transgression and sin, but who will by no means clear the guilty, visiting the iniquity of the fathers on the children and the children’s children, to the third and the fourth generation.” And Moses quickly bowed his head toward the earth and worshiped.Exodus 34:6-8
The glory of God compelled Moses to bow low and worship Him. God is our Maker and Master. He is the beautiful, holy, eternally good Creator of all things, and unto Him we owe utmost obedience. Notice also that Moses quickly worshiped God. There is no time to hesitate – no time for hiding (Genesis 3:8), explaining (1 Samuel 5:24-25), or self-preserving (John 3:20). You must this moment submit to God. You must right now bow down before Him.
Sin is such a grave, serious matter! We see the heinous character of sin only when we see the beauty and perfection of the one against Whom we sin, Whose law we have broken. As glorious as God is, so despicable is your sin. Therefore, do not treat sin lightly. There are no “small” sins, no “pet” sins, no “insignificant” sins. They are all monsters and venomous snakes. Harboring sin is like inviting an assassin to the dinner table. In one hand, he lifts his wine for a toast; in the other hand, he grips his dagger for your throat. Give no quarter to lawlessness.
Question: What is sin?
Answer: Sin is rejecting or ignoring God in the world he created, not being or doing what he requires in his law.
 Sin is relative to God, but to nothing/no one else.
 Legalism is the attempt to justify oneself before God on the basis of works. Attempting to live a holy life, and calling others to live a holy life, is not legalism. Moralism is adding to God’s law certain requirements which He has not identified.