Excellent post John. We all need to memorize those and practice them daily!!!
Onefaith, I've copied 6-10 together here because they all are one continuous thought:
If we say that we have fellowship with Him and yet walk in the darkness, we lie and do not practice the truth; 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 His Son cleanses us from all sin. If we say that we have no sin, we are deceiving ourselves and the truth is not in us. If we confess our sins, He is faithful and righteous to forgive us our sins and to cleanse us from all unrighteousness. If we say that we have not sinned, we make Him a liar and His word is not in us.
It's saying in 6 that if we claim to be a believer and yet walk in darkness (sin) we're lying and don't live the truth. And your verse continues on from 6 to say the contrasting view.......but those of us who truly are believers show it by walking in His light (deeds of righteousness), walking in obedience and when we do, we'll have true fellowship with one another - you can't have true fellowship with the one who lives in darkness, but only with those who live in the light. And the the blood of Jesus will continue to cleanse us from all sin as we continue on in obedience.
John is comparing those who say they are Christian with those who truly are Christians. The one walking in darkness will deny sin and their deceiving themselves by rejecting the truth. But those of us walking in the light, if we continue to confess our sins, He is faithful and righteous to forgive us our sins and to cleanse us from all unrighteousness.
It's the liar that says he has no sin and John is saying that the word of God isn't in that person, they walk in darkness, in lies and in disobedience and so there is no fellowship with these types of people.