An old post from 2004.
If we confess our sins, He is faithful and righteous to forgive us our sins and to cleanse us from all unrighteousness.
(1 John 1:9 NASB update)
Why would God’s righteousness be compromised if He did not forgive sin? This verse tells us, “He is … righteous to forgive.” Does confession create an obligation on the part of God to forgive, an obligation He’d unjustly violate if He didn’t forgive? Is His righteousness the same as His faithfulness, so that faithful and righteous is simply a more forceful expression of God’s commitment to fulfill His promise of forgiveness? What is the basis of our expectation of forgiveness—is it God’s righteousness or God’s benevolence? When we so readily quote this verse to assure ourselves, or one another, of God’s forgiveness, do we wonder at it?
We’d normally expect John to affirm God’s grace in forgiving sin, “He is faithful and gracious to forgive us our sins.” We normally appeal to God’s mercy for forgiveness in spite of God’s righteousness; not because of it. We recognize that God’s righteousness requires judgment, not forgiveness. We take great comfort from the first part of God’s self-revelation to Moses, “The Lord, the Lord God, compassionate and gracious, slow to anger, and abounding in lovingkindness and truth; who keeps lovingkindness for thousands, who forgives iniquity, transgression and sin;” but we tremble over the second part, “yet He will by no means leave the guilty unpunished, visiting the iniquity of the fathers on the children and on the grandchildren to the third and fourth generations” (Ex 34:6,7)
We know that “our unrighteousness demonstrates the righteousness of God” (Rom 3:5) not because God forgives but because He judges. He is Himself justified—shown to be personally righteous—when He pronounces judgment on sin. (Rom 3:4) In fact, God’s forbearance of sin raises questions about God’s own righteousness. Is He too pure to look upon sin, or not? Doesn’t He in fact tolerate sin? He may occasionally reveal His fury against irreverence, such as in His outburst against Uzzah (2 Sam 6:1-9), but more often He is silent. (When we read this shocking passage our reflex is to ask, “How can God do that?” though the question we ought to ask is, “Why doesn’t He do that all the time?” If God is so offended by the careless irreverence of a man simply reaching out to steady the ark of God, if this seemingly innocent act is worthy of death, then how is it possible any one of us continues to survive for a single second? We offend God, treating Him as less holy than He is every second of every minute of every day. How could God bring the flood to destroy the earth in the days of Noah when His evaluation of human character is the same immediately afterwards as before? The intent of man’s heart is evil from his youth. (compare Gen 8:21 with 6:5)) God must acquit Himself against the charge of too readily overlooking sin. He must prove His righteous revulsion against sin. (see Rom 3:25,26) It is strange for us to rely on His righteousness for assurance of forgiveness.
The key to understanding this verse is found in the first two verses of chapter 2, “And if anyone sins, we have an Advocate with the Father, Jesus Christ the righteous; and He Himself is the propitiation for our sins; and not for ours only but also for those of the whole world.” It is really found in the word, propitiation; it is because of propitiation that God’s righteousness is at stake in our forgiveness, that we can count on God to be righteous to forgive.
Propitiation refers to the work of Christ in averting the righteous wrath of God. It’s very important for us to be clear about how this works. The editors of the Revised Standard Version, for example, translated the Greek as “expiation” rather than “propitiation” because they thought the idea of propitiating the wrath of a personal god too heathen. A heathen worshipper appeases his angry god, in essence, by bribing him, by presenting an offering that’s valuable enough to convince his god that it’s preferable befriending him than harboring anger. But Christ’s offering is far from a bribe, and He does not propitiate God simply by changing His mind. Instead, He offers Himself—an infinitely valuable offering, it is true—not to divert God’s wrath and fury but to absorb it. Christ is our propitiation because God’s fury toward sin was fully unleashed on Him. It was fully expressed, given full vent, and exhausted. Jesus cried out, “My God, My God, why have You forsaken Me?” because He really had! Jesus felt the alienation from God, the wrath of God, our sins deserved. The resurrection proves to us that God’s wrath is removed. The Father receives His Son with a smile. If God had simply changed His mind about us, there’s no reason He couldn’t change it back. There would be no reason He couldn’t revert to His previous anger. But if, instead, He has fully punished our sins with infinite fury, then it would be wrong for Him not to forgive, “He is faithful and righteous to forgive us our sins.” There is no double jeopardy with God.
But if this is true, why is forgiveness conditional upon confession, “If we confess our sins, He is faithful and righteous to forgive … ?”
Christ’s propitiation is effective for those who are really united to Him. Faith is what unites us to Him so that His propitiation is for us. We might look at our union with Christ from two different perspectives. From God’s perspective, we are united with Christ in principle in election. This, then, is effected by His calling us and subsequently baptizing us with the Spirit into Christ. (1 Cor 1:30; 12:13) From the human perspective, it is faith that unites us to Christ. Our hearts, that is, all our affections, are drawn out toward Christ in love, trust, hope, and so on. Faith is an affectional union with Him. (I see little difference between loving God and believing Him.) Confession, too, is an expression of faith, and has the same dynamic, effecting a mental union with Him. To deny that we have sinned is to call God a liar. (v. 10) That is the very opposite of faith. Faith regards God as trustworthy; to deny that we have sinned is to accuse God of lying about us. It is to claim that His evaluation of us is untrue. On the other hand, to confess our sins is to agree with God’s testimony against us. We are of one mind with God about ourselves. Confession is a condition for forgiveness because union with Christ is a condition of His propitiation being for us, faith is what effects that union, and confession is an expression of that faith.
 He is given as the propitiation for the sins of the whole world in the same sense that “there is no other name under heaven that has been given among men by which we may be saved” (Acts 4:12) There is one name for the whole world; there is one propitiation for the world.