The beloved books of 1st, 2nd, & 3rd John were written by the Apostle John, who was one of the original 12 disciples. The authorship is not indicated in the text of the letters such as is found in the Pauline letters. Nevertheless, external evidence for the authorship of these three epistles by John is strong and without significant controversy.
The Apostle John wrote five New Testament books: the Gospel of John, 1st, 2nd, & 3rd John, and the book of Revelation.
John originally ministered in Jerusalem. Early church tradition tells us that he left Jerusalem (probably well ahead of the destruction of the temple in A.D. 70) and went to the Roman province of Asia. There he ministered in and around Ephesus and probably with all of the seven churches of Asia described in Revelation 2 and 3.
The date of writing was most likely about A.D. 95. John, the aged father of the churches wrote to his beloved children.
The purpose of John's writings was to reassure these Christians, who were living in a difficult pagan environment, that they were indeed the children of God. It was further an encouragement for these believers to love one another in true Christian fellowship. There were also warnings about both internal and external threats of false teaching, insincere Christian living, and the difficulty of sin in the believer's life.
Believers need to grasp and internalize what they are: Children of God! And the best is yet to come. When Christ returns, we shall be like him fully.
John saves some very important things for the close of this first letter. It is a crescendo of heart and mind as he gives them three tests (love, obedience, faith), three testimonies (water, blood, Spirit), and three assurances (eternal life, answered prayer, constant protection). What riches we have in Christ!
The issue of sin in the believer's life can be quite perplexing. John tells these believers what sin has done, what Jesus has done, and what salvation has done for us. Sin has ruined us. But Jesus appeared to take away our sins and to destroy the work of the devil. Salvation has made a radical difference in our lives.
What is the difference between worldly love and Christian love? Christian love is agape-love. This is something very distinctive. Agape-love makes it possible for us to love one another. Agape-love is here defined.
What is Christianity all about? It is about the God - Man, Jesus Christ. He is both perfect Man and perfect God.
As Christians we can sometimes be confused. We may feel guilty when there is no reason for guilt. False teachers from the cults will try to twist the truth. The opposing world gets strong in its influence. John attempts to encourage and strengthen these Christians to hold fast to their Christian faith.
John gives three ways to test the validity of our Christian faith: the moral test (obedience), the social test (love), and the doctrinal test (truth). There are antichrists. True Christians are sure on several levels that they are of God.
The term "worldly Christian" is really an oxymoron. There is not such thing. Christian conversion is a radical thing. Believers are not to love the world. If they do, then the love of the Father is not in them.
John gives us three great descriptions of God: God is Spirit (Gospel of John), God is Light and God is Love. Here John contrasts light (God) and darkness (sin). We cannot claim to be Christians if we walk in the darkness of sin.