Keeping mercy for thousands, forgiving iniquity and transgression and sin, and that will by no means clear the guilty; visiting the iniquity of the fathers upon the children, and upon the children’s children, unto the third and to the fourth generation. (Exodus 34:7)
What is the difference between the terms “iniquity,” “transgression,” and “sin”? There must be a difference for all three words to be used.
That there is a difference in meaning is obvious, just as you point out. And though the words are synonymous in the sense that they each can be used to generally denote or describe that which is contrary to God’s will, they differ especially in where they lay the emphasis.
“Sin” is the most fundamental of the three terms, denoting as it does the plain and simple fundamental issue of something being contrary to, or a violation of, God’s will. Hence when something is declared to be a “sin” that’s what it is: an act or deed that is contrary to God’s will; a violation of His will. We speak of men being ‘sinners’ by nature because by nature men do things that go contrary to God’s will; that violate His will. When, for example, Paul certifies the reality of both Jew and Gentile being “under sin” in Romans 3:9ff, he sets forth a specific listing of indictments from the Scripture that detail specific acts of contrariness to God’s will and violations of it. This, once again, is what the term “sin” conveys.
“Transgression” is usually used in contexts where God has set forth particular commandments that He wants kept, or particular prohibitions that He wants enforced. For this reason the term is commonly used in connection with the Law and we commonly speak of ‘transgressions of the law.’ As such the term denotes doing something that directly goes against conformity to what God said to do or not to do. And since “transgression” denotes the issue of going directly against what God said, it is the word that by its meaning is designed to make the transgressor aware of the fact that he has sinned. In other words the word “transgression” makes sin personal, so to speak. It makes someone realize that they have ‘gone out of the way’ that conforms to God’s Righteousness and Holiness, and they have done that because by nature they “sin.”
“Iniquity” is the term that denotes the offensiveness and repulsive nature that belongs to sin and all of its expressions. It is the term that describes the offensiveness of sin to God, specifically to His perfect Righteousness and Holiness. Hence “sin” is not only the violation of God’s will, it also is an offense to Him. He reacts to it. His perfect Righteousness and His pure Holiness abhors it. There is a revulsion to it, and “iniquity” is the term that stresses this aspect of things.
The contexts in which God uses each of the words governs the reason for why He uses one word instead of another, or why He uses them in combination.
For example in Exodus 34:7 all three words are used because all three issues are issues God wants Israel to be confronted with in view of entering into the Law covenant with Him. Simply put, they entered into that Law covenant because of their high-mindedness about themselves. They did not look upon themselves in truth. They thought themselves to be different by nature from Gentiles and that as such they were naturally fit to be utilized by God in His plan and purpose. They thought that they naturally were pleasant to God, pleased Him, being different from others. Moreover just previous to entering into the Law covenant they responded negatively to the issue of God educating them in their need for His “Jehovah-ness” and grace in view of the fact that they are not different by nature.
Hence when they entered into the Law covenant they entered into a relationship with God whereby they would end up ‘learning the hard way’ the truth about themselves. By means of the ministration of the Law they would learn the truth that they were sinners by nature, who transgress what God says to them, and who in doing so produce iniquity in God’s sight. Moreover they would also learn that if it was not for God being “full of mercy” and the like, and if it was not for His “Jehovah-ness” by which He would be able to forgive their “iniquity and transgression and sin,” they would never be able to be made fit to be utilized by Him in His plan and purpose.
– K.R. Blades