In St. John’s first letter, readers are given three self-tests that can make clear whether or not a person belongs to Christ and shares the life of the age to come. This, he says is why he wrote the letter: “I write these things to you who believe in the name of the Son of God so that you may know that you have eternal life” (5:13).
I’ve heard this verse presented as a stand-alone proof of the assurance of eternal life, but this verse clearly does not stand alone. John says, “I write these things to you … so that you may know you have eternal life.” The obvious question is: what things did he write? And the answer is, the three tests.
Each of the three tests is stated three times in the letter and with each repetition comes further elaboration. We could label one test the doctrinal test: Does a person believe that Jesus is God’s Son the Messiah who became truly human?
A second test is the life test. The person who has eternal life obeys God’s commands and pursues a Jesus-like life. This is not to say that person never sins. John knows that, apart from Jesus, anyone who claims to be without sin is self-deceived (1 John 1:8). People who pass the life-test aren’t perfect but they confess their sins and deal with them. They desire to be like Jesus and they take steps to make it so (3:1-4).
The third test could be called the social test. The first test is over what we believe. The second test is over how we live. The third test is over who we love. The person who has the eternal kind of life loves God and loves Jesus’s people.
One more thing about the three tests: they overlap a great deal. A person who is growing in faith will be growing in obedience as well. A person who grows in obedience will be getting better at loving other people. This overlap, which is mentioned numerous times in 1 John, is crystalized in a single verse in 3:23: “And this is his command: to believe in the name of his Son, Jesus Christ [doctrinal test], and to love one another [social test] as he commanded us [life-obedience test].”
That Jesus’s people love each other is a critical component – along with the calling of a people, the giving of the law, the incarnation of God, the death and resurrection of Christ, and the impartation of the Spirit – in God’s plan for the world.