Again, I write a new commandment to you, which is true in him and in you; because the darkness is passing away, and the true light already shines.
Now, he is talking about the purpose of writing is to bring you into fellowship with God, but the thing that breaks fellowship with God is sin. In Isaiah 59 , "God's hand is not short that he cannot save, neither is his ear heavy that he cannot hear. But your sins have separated you from God" ( Isaiah 59:1-2 ). Always the effect of sin. God said to Adam, "In the day that thou sinneth thou shall surely die." And Adam sinned, and God came into the garden, and He said, "Adam, where art thou?" Fellowship with God had been broken as the result of sin, always is. So, in order that you might have fellowship with God, it is necessary that we sin not. And John is writing that you might have power over sin. And the power over sin, of course, comes through the abiding of the Holy Spirit within our lives. "These things have I written unto you, my little children," or, "These things write I unto you that you sin not."