“Whoever does not love does not know God, for God is love.” (1 Jn 4:8).
Who were these letters written for? Similarities between the gospel of John and the letters of 1, 2, and 3 John have led many scholars to believe they all were written for and from a single early Christian community (often referred to as “the Johannine community”). The gospel and the different letters are put together to address various crises the community faced over time.
Though traditionally considered a letter, 1 John is really more like a sermon (a good one!). References to a group of people who “went out from us,” antichrists who deny “Jesus Christ has come in the flesh” (2:18-27; 4:1-3), suggest it was written to oppose a type of Christian thinking called Docetism. The author wants the community to know that Jesus walked and talked and was as physically real as anyone.
Unlike 1 John, 2 John is an actual letter from an elder to “the elect lady and her children,” probably a reference to a certain Christian congregation and its female leader (see 2 Jn 13). Similarly to 1 John, 2 John seems to represent opposition to a group with Docetic tendencies, (2 Jn 7). Uncharacteristically, the letter exhorts its recipients to totally avoid such people.
Like 2 John, 3 John is also an actual letter from an elder to a person called Gaius. The letter commends Gaius for “walking in the truth” (3 Jn 3), and for his hospitality to strangers. It condemns someone named Diotrephes for insubordination, spreading lies, and standing in the way of the Christian community all three letters praise.
1 and 2 John strongly insist on the need for Christians to love and welcome other Christians (see 1 Jn 4:8; 2 Jn 5-6; 3 Jn 10). In fact, it is a preeminent and abiding theme of the entire group of letters making them good reading for anybody.