We need to admit that after regeneration we still have sin; that is, we still have indwelling sin in our sinful nature. Because we still have sin within us, there is the possibility that we may sin. Whenever we sin, we need to confess. Then God will be faithful in the word of His new covenant to forgive us our sins. In the gospel, which is the new covenant, God promises that He will forgive us our sins because of the redemption of Christ. Therefore, if we confess our sins, God must be faithful to keep His word. If God would not forgive us, this would mean that He contradicts His own word. In such a case, God would not be faithful. However, we may have the assurance that as long as we confess our sins through the redemption of Christ, God must forgive us, for He must be faithful in His word.
In verse 9 John also tells us that God is righteous to cleanse us from all unrighteousness. Why must God be righteous to cleanse us in this way? God must be righteous to cleanse us from unrighteousness because He judged the Lord Jesus on the cross as our Substitute, putting all our sins upon Him. Because God has judged Christ for us, His blood is efficacious to cleanse us. Therefore, when we confess our sins through His blood, God has no choice but to forgive us. For example, suppose you owe an amount of money to a certain person. A friend of yours pays this debt for you, and the other party receives the payment. Now that party cannot righteously claim the payment from you, for the debt has already been paid. In a similar way, God has received payment for our sins through the death of Christ on the cross. Now whenever we confess our sins to God through the blood of the redemption of Christ on the cross, God must forgive us. In this matter He has no choice. He must be righteous.
God is faithful in His word, and He is righteous in His acts. In His word God must be faithful, and in His acts He must be righteous. Here we see the difference between faithfulness and righteousness.
What is the difference between forgiving and cleansing? In order to know this difference, we need to know the difference between sins and unrighteousness. Sins refer to offenses, and unrighteousness is the mark, the stain, on our behavior caused by the committing of an offense. Whenever we sin, we commit an offense. This offense then becomes a stain on our behavior, and this stain is unrighteousness. For instance, suppose you buy two items, but you are charged only for one. If you pay for just one item, that will be an act of sinning against the store. With respect to the person who sold you the items, that is an offense. But with respect to your character, that is a mark of unrighteousness. For this reason, others would not say that you are sinful, but would say that you are unrighteous.
In a similar way, when we commit sins before God, with respect to God those sins are offenses. But with respect to us, they are stains of unrighteousness. We need to confess our sins. Then, on the one hand, God forgives our sins, our offenses. On the other hand, God washes away the mark, the stain, of our unrighteousness. This is the reason John in 1:9 speaks both of the forgiveness of sins and the cleansing from unrighteousness. The forgiveness of sins is actually the cleansing, the washing away, of the stain of our unrighteousness.
The writing of the apostle John in these verses is tender and delicate. In verse 6 he says, “If we say that we have fellowship with Him and walk in darkness, we lie and are not practicing the truth.” Then in verse 8 he goes on to say, “If we say that we do not have sin, we are deceiving ourselves, and the truth is not in us.” In verse 10 he says, “If we say that we have not sinned, we make Him a liar, and His word is not in us.” But in verse 9 John tells us, “If we confess our sins, He is faithful and righteous that He may forgive us our sins and cleanse us from all unrighteousness.” God is faithful in His word to forgive our offenses, and He is righteous in His acts to cleanse away the stain of unrighteousness. Through God’s forgiveness and cleansing, the offense is forgiven, and the mark is cleansed. The result is that our fellowship with God is fully recovered.
Fellowship with God is broken by sin and unrighteousness. But when sin is forgiven and the stain of unrighteousness is cleansed, our fellowship with God is restored. Once again we have the enjoyment of the divine life through our fellowship with the Father and the Son.