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That which was from the beginning, which we have heard, which we have seen with our eyes, which we have looked at and our hands have touched—this we proclaim concerning the Word of life.
The life appeared; we have seen it and testify to it, and we proclaim to you the eternal life, which was with the Father and has appeared to us.
We proclaim to you what we have seen and heard, so that you also may have fellowship with us. And our fellowship is with the Father and with his Son, Jesus Christ.
We write this to make our joy complete.
This is the message we have heard from him and declare to you: God is light; in him there is no darkness at all.
If we claim to have fellowship with him yet walk in the darkness, we lie and do not live by the truth.
But if we walk in the light, as he is in the light, we have fellowship with one another, and the blood of Jesus, his Son, purifies us from all sin.
If we claim to be without sin, we deceive ourselves and the truth is not in us.
If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness.
If we claim we have not sinned, we make him out to be a liar and his word has no place in our lives.

GNT … If we claim to be without sin, we deceive ourselves and the truth is not in us.
If we confess our sins, he is faithful and just and will forgive us our sins and purify us from all unrighteousness.
If we claim we have not sinned, we make him out to be a liar and his word is not in us.

John is telling us, we may enter into the same close partnership with the Father and the Son. But no impurity or insincerity is permissible to those who enter that fellowship.

Our one aim should be to maintain such a walk with God that the union with God may be unimpaired. If there are still sins of ignorance, the blood of Jesus will continue to remove them. Sin differs from sins, just as the root from the fruit. God does not only forgive, He cleanses and is faithful to His promises