One of the most helpful pieces of advice on reading the Bible that I have been given is this: 'Always look for the suprises'. That is, always be on the look out for things that you wouldn't expect the author to say or ways you didn't expect him to say it.
One such suprise comes in a very familiar couple of verses. 1 John 1:8-9 says this: "If we say we have no sin, we decieve ourselves, and the truth is not in us. If we confess our sins, he is faithful and just to forgive us our sins and to cleanse us from all unrighteousness."
Did you notice the suprise? If we were writing these verses it is very likely that we would not have said that God is "...faithful and just to forgive us our sins". It's more likely that we would have said something like: 'He is gracious and merciful to forgive us our sins' (which we know from the rest of Scripture is gloriously true). So why then does John say that God is faithful and just to forgive our sins? How does His faithfulness and justice relate to His forgiveness of sins? What difference does it make to our understanding of forgiveness? I want to suggest that it makes a huge difference.
Let's look at both of these ideas individually:
1) God is faithful to forgive us our sins
Why is it that God is faithful to forgive us our sins? He is faithful because He has promised to forgive. He has promised His people "...I will forgive their iniquity, and I will remember their sin no more." (Jeremiah 31:34), and has fulfilled this in Christ (see Hebrews 10:1-18 - especially v 17). He has promised that all those who look to Christ in repentance and faith have their sin forgiven.
This means that we can have great assurance therefore of forgiveness, because of who has promised. God does not lie, nor does He change His mind, therefore what He has promised is sure and certain. He has promised forgiveness of sin to all those who trust in Christ. Therefore, as His people, we have confidence that "If we confess our sins, he is faithful... to forgive us our sins".
2) God is just to forgive us our sins
This is probably the more suprising of the two suprises. In what sense is God just to forgive us our sins? The rest of the context of 1 John helps us to understand this. The answer is found in the work of Jesus. In 2:1-2 we read "...if anyone does sin we have an advocate with the Father, Jesus Christ the righteous. He is the propitiation for our sins...". God had given Jesus to us to be the propitiation for our sins, He is the one who has turned aside God's wrath from us by willingly taking it upon Himself in our place. He is the righteous one who took our unrighteousness upon Himself, taking its consequences on the cross. It is through faith in Him that we are counted as righteous.
This means that Jesus can be our advocate. He stands before the Father in our defence, pleading that He would deal justly with us and forgive us. He can do this because justice has already been done at the cross. Our sin has already been punished at the cross, and God will not punish the same sins twice.
When we do sin, we have the confidence to come before God and plead that He would act justly towards us and forgive us our sin. We have the confidence to do this because of the cross. As His people, the punishment for our sin has been poured out on Jesus in our place , therefore we shall never have to bear it. The hymnwriter Augustus Toplady puts it like this:
If thou hast my discharge procured,
And freely in my room endured
The whole of wrath divine;
Payment God cannot twice demand,
First at my bleeding Surety's hand,
And then again at mine.
God will not punish the same sins twice. If the punishement has already been taken by Christ on the cross, we have complete assurance that we shall never have to bear it.
Surely this brings us great assuance. We can humbly and confidently confess our sin before God and ask for His forgiveness, knowing that He will forgive. John is quite clear that this truth is not an encouragement to sin (1 John 2:1), but it is an encouragement when we do sin. Which we will do (1 John 1:8) until that day when "...we shall be like him, because we shall see him as he is." (1 John 3:2).
When we understand these truths we can go away joyfully singing the final verse of Toplady's hymn: