John Calvin Commentary 1 John 1:9

"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 (ASV)

If we confess, He again promises the faithful that God will be gracious to them, provided they acknowledge themselves to be sinners. It is of great importance to be fully persuaded that, when we have sinned, reconciliation with God is ready and prepared for us; otherwise, we will always carry a hell within us.

Few, indeed, consider how miserable and wretched a doubting conscience is; but the truth is that hell reigns where there is no peace with God. Therefore, it is all the more incumbent on us to receive with our whole heart this promise, which offers free pardon to all who confess their sins. Moreover, this is founded on the very justice of God, because God who promises is true and just. For those who think that He is called just because He justifies us freely are, I think, reasoning with too much subtlety, because justice or righteousness here depends on faithfulness, and both are linked to the promise. God could have been just if He were to deal with us with all the rigor of justice; but since He has bound Himself to us by His word, He would not have Himself considered just unless He forgives.

But this confession, since it is made to God, must be sincere; and the heart cannot speak to God without newness of life. It therefore includes true repentance. God, indeed, forgives freely, but in such a way that the ease of mercy does not become an enticement to sin.

And to cleanse us. The verb to cleanse seems to be taken in a different sense than before; for he had said that we are cleansed by the blood of Christ, because through Him sins are not imputed. But now, having spoken of pardon, he also adds that God cleanses us from iniquity, so that this second clause is different from the preceding one. Thus, he indicates that a twofold fruit comes to us from confession: first, that God, being reconciled by the sacrifice of Christ, forgives us; and second, that He renews and reforms us.

If anyone were to object and say that as long as we live in the world, we are never cleansed from all unrighteousness regarding our reformation—this is indeed true. But John does not refer to what God is now performing in us. He is faithful, John says, to cleanse us—not just today or tomorrow. For as long as we are surrounded by flesh, we ought to be in a continual state of progress. But what He has once begun, He continues to do daily, until He finally completes it. So Paul says that we are chosen so that we may appear without blame before God (Colossians 1:22); and in another place he says that the Church is cleansed so that it might be without spot or wrinkle (Ephesians 5:27).

Yet, if anyone prefers another explanation—namely, that he is saying the same thing twice—I will not object.