John discusses the first of two major themes about the nature of God – God is light.  John shows how this truth about God has ramifications for those who claim to be His.

5-7 
John says the message we have heard from Him – the Word of Life (Christ) – is that God is light.  This is similar to what he said at the beginning of his gospel – In Him was life, and the life was the light of men.  And the light shines in the darkness, and the darkness did not comprehend it (John 1:4-5).  There he referred to Jesus as the light.  Here he says that Jesus pointed to the Father as the light.

Light refers to God’s character – His perfection and holiness and righteousness.  It also refers to His glory and splendor (Paul defines it as unapproachable light – I Tim 6:16).  That He is light also means He is the source of light for all mankind – it is why Jesus could say, “I am the light of the world” (Jn 8:12), and why John said Jesus was the light of men (Jn 1:4), and why Paul called us sons of light and sons of day (I Thess 5:5).

Note that John does not say that God is in the light or that He walks in the light; he says that God IS light.  It is His very nature – it’s who He is.  WE may walk in the light.  WE may practice righteousness.  He IS light and He IS righteousness.

If God is light, then it follows that in Him there is no darkness at all.  Light can’t be dark – it’s impossible by definition.  Darkness is the absence of light.  Darkness is not defined by what it is but by what it isn’t – it is not light (the same as cold is not heat – and in both cases they weren’t created – darkness and cold are what exist without light and heat).  Therefore it can’t exist in God because He IS light.  If the nature of God included or permitted darkness, then He would not be light – He would merely exist in light periodically.  To BE light means that darkness does not and cannot exist in God’s essence.  John wants his readers to understand that a mark of the transcendence of God is that He IS the opposite of sin.

What are some of the characteristics of light?  Light reveals.  Light shows the way forward clearly.  Light gives joy and hope and confidence.  Nothing hides in light.  There are no regrets in light because ulterior motives and deception cannot exist where everything is revealed.  There is no fear in light – there is no such thing as being “scared of the light.”  Light leads to awareness and watchfulness – people do not sleep in the light.

Verse 6 makes a logical deduction from verse 5.  If we walk in darkness we can’t say we have fellowship with God.  Darkness can’t fellowship with light when by definition it doesn’t exist where light is.  Those who make the claim to walk with God are lying if they walk in darkness.

By walk, John seems to be referring to a way of living.  It’s what typifies an overall life – the habits and actions that make up the character.  He does not mean someone who doesn’t sin – he will make that clear in the next verse.  He means the comprehensive makeup and direction of a believer’s existence.  It is similar to Jesus’ words in the Sermon on the Mount when He said that good trees only bear good fruit and cannot produce bad fruit (Matt 7:17-18).

John says not only that we lie when we walk in darkness but that we do not practice the truth.  Our practice, what actually makes up our life, is a lie in itself.  Our actions show that our claim is false.  The truth is that we do NOT have fellowship with God and our practice bears this out.

Thought: What does it mean to walk in darkness?  It means not seeing as God sees.  One who walks in darkness doesn’t recognize the truth and thus doesn’t practice it.  He desires the rewards and temptations of the world more than God because they look better out of the light.  He believes the deception that what’s in front of him is better than anything God has to offer.  He lives a life of deceit; both deceiving himself and others.  And he hates light because darkness to him is truth and light is the opposite of all that he loves.  That’s why he can’t claim fellowship with God.  John explained this in his gospel: And this is the judgment, that the light is come into the world, and men loved the darkness rather than the light; for their deeds were evil.  For everyone who does evil hates the light, and does not come to the light, lest his deeds should be exposed (Jn 3:19-20).

BUT if we walk in the light as He Himself is in the light, we have fellowship with one another, and the blood of Jesus cleanses us from all sin.  When we walk in the light and practice the truth we have fellowship with others who do the same and our sins are cleansed by the blood of Christ.  Here is where it’s clear that walking in the light does NOT mean we don’t sin – it means our lives are not characterized by the darkness of sin and our sins are CLEANSED by Christ’s blood.  Those who walk in the darkness – though they claim fellowship with the light – do not have true fellowship with others in the light and their sins are NOT cleansed (this backs up verse 6 – we can’t claim to be justified by Christ’s blood if we walk in darkness).

We expect verse 7 to say when we walk in the light we have fellowship with GOD – that’s what seems to follow the point of verse 6.  But John says we have fellowship with one another.  This seems to hearken back to verse 3 where he says his motive for proclaiming the gospel is fellowship with other believers who share fellowship with the Father and Son.  Fellowship with God is through prayer and study but also through fellowship with other believers.  Thus fellowship with others and fellowship with God are synonymous when that fellowship is based on God’s light.  This also means that true fellowship with others is impossible apart from walking in the light.  Our fellowship with each other can be similar to our fellowship with God, and our fellowship with God can be similar to our fellowship with each other.  We can walk and commune and pursue on a level far beyond what most of us can imagine.  So verse 7 teaches that the only way to preserve the precious jewel of deep unity with God and with other believers is to walk in the light—to see things in the light of God, to let God be your bright pathway to joy.  (John Piper, Sermon on I John 1:5-10; 02/03/85.)

Thought: What does it mean to walk in the light?  It means we see as God sees.  We see the world, the flesh and the devil for what they are.  The passing pleasures of sin look less and less enticing.  Our thoughts and motives become clear so we regularly confess sin (vs 9).  As the world sparkles less we anticipate Christ’s return more (I Thess 5:2-11) and live for eternity.  As exposure and confession shrink the dark areas of our lives, we become increasingly pure in heart (Matt 5:8) with our deeds wrought in God (Jn 3:21).  And the longer we walk in it the more we love the light and practice the truth and can’t imagine living any other way.

That the blood of Christ cleanses our sins seems to refer to justification with implications for sanctification.  We are justified by Christ’s sacrifice on the cross.  But His blood also enables us to say no to sin and become more and more conformed to His image (notice that cleanses is in the present tense).  We are no longer under the power of sin because of His blood (Rom 6).  It’s why John can also say in verse 9 that He cleanses us from all unrighteousness.

8-10
If our sins are cleansed by the blood of Christ, then to say that we have no sin is to deceive ourselves and show that the truth is not in us.  Everyone sins – even those who fellowship in the Light.  Jesus’ blood cannot cleanse our sins if our sins don’t exist.  It is only those who walk in the darkness – and deceive themselves (note the agent of their deception) – who think they do not sin.  BUT if we confess our sins, He is faithful and righteous to forgive us our sins and to cleanse us from all unrighteousness.  Those who walk in darkness don’t confess sin because they can’t confess what doesn’t exist.  Note John says the truth is not in us – this is beyond even the thought in verse 6 that we do not practice the truth.  Those who deny their own sin do not have the truth – in simple terms they are not believers.

The answer to the wrong thinking of verse 8 is the practice of verse 9.  Thus a distinguishing characteristic of walking in the light is ongoing confession of sin.  Those who walk in the light see the world as God sees it and see sin as God sees it.  As they enter into the light more and more their sins are exposed more and more.  And their God-aligned hatred of sin causes them to confess it and turn from it.  And the wonderful promise of walking in the light through the blood of Christ is that HE WILL FORGIVE US OUR SINS AND CLEANSE US FROM ALL UNRIGHTEOUSNESS.  This is God’s promise to those walking in the light.  This is the power available to those fellowshipping with the Father and with the Son.  He will restore us to fellowship when we confess our sins.  He will forgive us and cleanse us.  Repentance is one of the Christian’s highest privileges.  A repentant Christian focuses on God’s mercy and God’s grace.  Any moment in our lives when we bask in God’s mercy and grace is our highest moment.  Higher than when we feel smug in our decent performance and cannot think of anything we need to confess.  (Mutua Mahiaini; quoted in The Discipline of Grace, Jerry Bridges; 27)

And note – He is faithful and righteous in forgiving us.  He doesn’t forgive because He’s nice or because He’s willing to overlook the sin of certain people.  He forgives us because we are justified by Christ’s sacrifice (it’s why verse 9 comes after the truth of verse 7 – the blood of Jesus His Son cleanses us from all sin).  To not forgive would be unjust.  Our sin has been punished – ALL of it.  Thus the sin we confess has already been paid for and He can justly release us from it.

[Does the fact that God has forgiven us all our sins mean that He no longer cares whether we obey or disobey?  Not at all.  The Scripture speaks of our grieving he Holy Spirit through our sins (Ephesians 4:30).  And Paul prayed that we “may please [God] in every way” (Colossians 1:10).  We grieve God and we please God.  Clearly, He cares about our conduct and will discipline us when we refuse to repent of conscious sin.  But God is no longer our Judge.  Through Christ He is now our heavenly Father who disciplines us only out of love and only for our good. (Jerry Bridges, The Discipline of Grace; 18.)]

Verse 10 is similar to verse 8 except instead of making the error of saying “I have no sin” this person claims to have no specific sins (we have not sinned) for which he needs forgiveness and purification.  John says that beyond simply deceiving himself this person actually calls God a liar.  God knows we sin (“If you then, being evil…” – Matt 7:11) and to claim otherwise is to blaspheme and to show that His word is not in us – to show we are not His.  Said another way, when our lives are not characterized by ongoing confession of sin, then apparently we don’t feel we have sins to confess and we effectively tell God He’s lying about our sinfulness.

Note the structure of this passage
God is light and in Him is no darkness at all.
If God is light, and we say we have fellowship with Him and yet walk in darkness,              we lie and do not practice the truth.
BUT if we walk in the light we have fellowship with each other and the blood of                  Jesus cleanses us from all sin.
If the blood of Jesus cleanses us from all sin, then to say we have no sin means                    we are deceiving ourselves and the truth is not in us (we walk in darkness).
BUT if we confess our sins, He is faithful and righteous to forgive us our sins                        and to cleanse us from all unrighteousness.
If we do not confess our sins we must believe that we have no sins to                                      confess which means that we call God a liar and His word is not in us (we                              walk in darkness).

Characteristics of those who walk in the light

• Fellowship with others and with God.
• Truth in words and walk.
• Awareness of sin and the need for regular confession.
• Power of Christ’s blood to overcome sin.

Implications of walking in darkness

• No fellowship with others.
• No awareness of or cleansing from sin.
• No practice of truth.
• No understanding of God’s word.

The Christian religion is the religion of sinners, of such as have sinned, and in whom sin in some measure still dwells.  The Christian life is a life of continued repentance, humiliation for and mortification of sin, of continual faith in, thankfulness for, and love to the Redeemer, and hopeful joyful expectation of a day of glorious redemption, in which the believer shall be fully and finally acquitted, and sin abolished forever.  (Matthew Henry, A Commentary on The Whole Bible; Vol 6, 1063.)