‘If we confess our sins, he is faithful and righteous to forgive us our sins, and to cleanse us from all unrighteousness.'
The way to deal with sin is not by denying it or hiding from it, but by being open to the God Who is light. Then we can bring to Him those sins that grieve Him, that are revealed by His light, openly admitting them and acknowledging them to Him, and then know that He is the faithful God, the One Who is true to His promises and to His covenant with us, and that He will justly forgive our sins and cleanse us from all unrighteousness. The last fact is most important, ‘all unrighteousness'. He does not just forgive the sins of which we are aware, but also those of which we are unaware. When we are open with Him He cleanses us from all unrighteousness.
The word for ‘confess' means ‘say along with'. To ‘confess your sins' means to say along with God how He views your sins. To join in with Him in His decision about them. To agree to see them as God sees them, as they are, and not to seek to dismiss them as merely blunders or errors without a moral significance. Thus to be honest and open with God about them. Being open about moral failure is the first step to being free of it.
Note first here the stress on the faithfulness of God. If we are His He constantly watches over us and He is faithful to us, for He has brought us within His covenant (see 1 Corinthians 1:8-9) and we are His. And because of that faithfulness forgiveness is assured. There can be no room for doubt. For He Who made the provision for our sin through the shedding of His blood, will also faithfully apply it when we call on Him, to remove every blot and every stain (1 John 2:2). Then we will not only be forgiven, but will be made fully clean. It is a day by day cleansing, and it is complete.
And note secondly that God does it justly. There is here no casual overlooking of sin. He Who is light cannot be casual about sin. He is rather able to cleanse us from sin because it has been borne by another. God does not go against His own righteousness in forgiving, for He has Himself ensured that the guilt of that sin has been placed on the One Whom He sent as Saviour of the world (1 John 4:14). ‘He has made Him sin for us, He Who knew no sin, that we might be made the righteousness of God through Him' (2 Corinthians 5:21). ‘Who His own self bore our sins in His own body on the tree' (1 Peter 2:24). For when Christ died, we who are His died in Him, and through Him therefore we have paid the price of sin and have been given resurrection life (Galatians 2:20).
But that forgiveness, while in one sense once for all (Hebrews 10:10-14), because we have been sanctified by Him, must be constantly applied because we still continue as sinners in our flesh. And here the assurance is given that when we are continually totally open with God about our sins His blood continually cleanses (present tense) us from all sin and delivers us from all unrighteousness.
We note here that God does not demand great things of us. He does not call on us to in some way do a great penance for what we have done wrong. He does not demand great sacrifices. He recognises what we are and He freely forgives. And all that He requires of us is that we are open with Him and bring our sins openly to Him and seek his forgiveness and cleansing, with the determination to as far as possible be done with sin (1 John 3:5-6) and to walk in His light. Forgiveness, at least to us, is free, although to God it was very costly, for it took the life of His Son.
This may then raise the question, does this mean that we can then continue in sin so that God's forgiveness can abound? John answers that question immediately in 1 John 2:4. Those who truly know God will not even think like that. They know Him as the light and they want to be like Him. They want to walk in His light. No one who deliberately disobeys His demands can say that they ‘know Him'. Indeed it must be so for He is light. Paul answers the same question even more strongly from a different angle. ‘God forbid!', he says, ‘shall we who are dead to sin live any longer therein?' (Romans 6:2). The words here are of great comfort to the weak sinner who weeps over his sin and longs to be free from it, and yet seems constantly to stumble in it. He knows that there is a fount of forgiveness constantly open for him in his need. But they are no comfort at all to the complacent sinner. The latter will rather one day hear the voice that will say, ‘Why do you call me ‘Lord, Lord', and do not do the things which I say?' (Luke 6:46). He said that the ruin of their house will be great (Luke 6:49).
This is not a question of earning salvation by the way we live. To make such an effort would be the utmost folly. We would finish up crying with Isaiah, ‘Woe is me, for I am undone'. It is but to recognise that those whom Christ begins to save must change because He will ensure that it will be so. It is to recognise that those who come to the light must necessarily be affected by the effect of that light. All we can do is respond to His work within us because His Spirit enables us, and even that is through God's working (Philippians 2:13) but the work of His Spirit is never ineffectual and therefore the effects will be seen, and John is describing them here.