John ends this general letter reminding us of the same reason he wrote the Gospel account. Namely, that we can know without a doubt that we who believe in Jesus have eternal life. Because of that fact we can be completely confident that praying according to the known will of God results in answered prayer. He concludes by admonishing us to keep away from idols.
The apostle John primarily writes about two topics in these passages. The first is primarily on faith and how it is interconnected with love. To have real faith, you will love God and love others. And to have real love for God, you will follow His commandments. And the second has to deal with the testimony and witness for the truthfulness of the Gospel of Jesus Christ. Namely that God Himself has testified to it, and as a result, if we reject His testimony, we call Him a liar.
There are some key differences between children of the devil and children of God. Children of God have stepped out of death and into life whereas children of the Devil remain in death. Children of God love whereas the children of the devil hate. In addition, children of God abide in the Father, and the Father abides in them. As a result of this, we are different, and how we live our lives should be a reflection of this. Our lives should be characterized by love. And not just saying we love, but there should be actual evidence of our love in our deeds and actions.
As we study the first part of chapter 2, John is addressing something that all Christians need to understand. It is something that is just as relevant to us as it was to these believers 1900 years ago. Christians should not sin. We are to walk in the light and we are to obedient to Him.
John is writing a group of believers that have been assaulted with false teachings of claims contradicting the deity or humanity of Jesus. In addition some were claiming that they were not sinners or that sin didn't matter. John begins refuting these claims in this first chapter.