1 John 1:5

1 John 1:5 says, This then is the message which we have heard of him, and declare unto you, that God is light, and in him is no darkness at all.  John said that the message that he received from God and proclaimed to them is that God is Light and in Him there is no darkness.  If we are going to proclaim God's word, it must come from Him, and we can never accuse God of doing anything evil.    

Verse six adds, If we say that we have fellowship with him, and walk in darkness, we lie, and do not the truth:  John then said if we profess to follow God and walk in the darkness of the world, that we lie and God's truth is not in us.  If we are a true follower of Christ, we cannot continue to willfully sin at all times, though we might occasionally be guilty of some temporary sin, and if we are, we need to confess it to God and ask His forgiveness and turn away from the sin.  

Verse seven continues, But if we walk in the light, as he is in the light, we have fellowship one with another, and the blood of Jesus Christ his Son cleanseth us from all sin.  John then tells us that if we walk in the Light, and Jesus Christ is the Light, then we have fellowship with other believers.  We all do this by putting our faith in Jesus Christ, Who's shed blood cleanses us from all unrighteousness or sin.  We are cleansed from all sin for all time if we put our faith in Him.   

Verse eight states, If we say that we have no sin, we deceive ourselves, and the truth is not in us.  John tells us that if we say we have no sin in our lives to be forgiven, then we lie to ourselves and the truth of God is not in us.  Not only did Jesus say He was the Light, He also said He was the truth, so if we do not ask Him for forgiveness from our sins, the Truth cannot be in us.  

Verse nine adds, If we confess our sins, he is faithful and just to forgive us our sins, and to cleanse us from all unrighteousness.  John tells us that if we confess our sins and accept God's redemption through faith in Jesus Christ, that God is faithful to forgive us.  We cannot be a part of God's kingdom if we say we have never sinned and have no need of forgiveness.  

Verse ten continues, If we say that we have not sinned, we make him a liar, and his word is not in us.  John then added that if we say that we have not sinned, then we make God a liar, since He said all have sinned and come short of the glory of God, except for one Man, Jesus Christ.