Then Jesus spoke to them again, saying, I am the light of the world. He who follows me shall not walk in darkness, but will have the light of life. -John 8:12
We turn our attention to the full context of "light" and "darkness" in 1 John. We noted last time that the "cleansing" of 1 John 1:9 is a continual action. That helps us see the "confessing of sin" in the past tense. All sin was taken away by the cross ("the lamb of God who takes away the sin of the world... it is finished"). God has reconciled the world to himself through Christ (2 Cor 5:18). But we experience that past act as a present condition.
Something like: "If we are counted among those who have confessed they are sinners and were cleansed, he is faithful and is continually cleansing us from sin."
When we widen out from that verse, it starts to become clearer still.
Verse 8: If we say that we have no sin, we deceive ourselves, and the truth is not in us.
Everyone who is of the truth hears My voice. - John 18:37c
But you do not have His word abiding in you, because whom He sent, Him you do not believe. - John 5:38
Verse 10: If we say that we have not sinned, we make Him a liar, and His word is not in us.
This is not a warning that one can have light, then lose it. It is a clarification and comforting reminder to the believer. In that age (and the focus of John's ministry as an apostle to the circumcision), these are Jews who were cleansed from the condemnations and unrighteousness resulting from the law.
John writes (1:1-4) that he seeks the fellowship of fellow believers because all are in Christ and all have eternal life. He tells them he is wring to them "that your joy may be full." Those to whom John ministered could not lose "life" (it has always been a free gift), but they could be "disqualified" (2 Cor 9:27) or even lose the inheritance of the kingdom (1 Cor 6:9, parables of the kingdom, etc.).
Verses 5-7 lay out the basis for fellowship: they are all "in the light" and the blood of Christ continually cleanses them from all sin.
Verses 8-10 explain the difference between a true believer and a false believer. This clarification is evident in 1 John 2, culminating is verse 19:
They went out from us, but they were not of us; for if they had been of us, they would no doubt have continued with us: but they went out, that they might be made manifest that they were not all of us.
Backing up a little in 1 John 2, we read:
My little children, these things write I unto you, that ye sin not. And if any man sin, we have an advocate with the Father, Jesus Christ the righteous: And he is the propitiation for our sins: and not for ours only, but also for the sins of the whole world...
-1 John 2:1-2
We see, again, that sins are continually considered cleansed. John then returns to light and darkness:
He who says he is in the light, and hates his brother, is in darkness even until now. He that loves his brother abides in the light, and there is none occasion of stumbling in him. But he that hates his brother is in darkness, and walks in darkness, and knows not whither he goes, because that darkness has blinded his eyes.
-1 John 2:9-11
We will find fellowship with other believers. There are "professing" Christians who truly hate the light. They claim Christ, but oppose and blaspheme true believers. These are those who either never enter among us or, as we see in verse 19, go out from among us at some point.
We may have clashes with individual Christians, but we do not condemn true believer as a whole. In our age, this calls to mind the instruction in Ephesian 4:3, "keep the unity of the Spirit in the bond of peace." It is not a "created" unity by man, it is the maintaining of a unity created by God. This particular unity is given to the Body in this age:
"There is one spirit. When the Spirit seals and indwells, there is no room for other spirits. This is the true unity God desires for all, but is enjoyed only by His body. There is one calling to the body. The body is the called out assembly. Those believing ones are called out of the miasma of the world to walk the walk of those who please Him." -Jack Eberle
There is a dispensational difference here. The "unity" of this age is unique, but we can see some parallels with John's instructions. True believers in Christ (those baptized into his death) will, in the new nature, seek fellowship with the like-minded. We naturally love the brethren. I know some who naturally hate true believers while claiming to be Christian.
We also see a parallel in Paul's admonition that we go on to "the unity of the faith" (Eph 4:13). In contrast to the "keeping" of verse 3, this unity is achieved through seeking perfection (maturation). It is also unique to the Body, but, in any age, as believers come to a greater knowledge of the truths of that age, there will be a unity of faith. A truth for all ages:
Behold, how good and how pleasant it is
For brethren to dwell together in unity!
I will close this study here. I still have much reflection to do on this book and I may revisit it again in the future. But for now, I look back at 1 John 1:9 and say again that it is wonderful to know that the blood of Christ continually cleanses (current and past act) those who have come into the light of Christ by faith in his name!