Recall that John gives a cycle of tests for genuine Christianity. That three-fold cycle includes righteousness, love, and doctrinal integrity, and in this place he begins working his way through this cycle for a second time. A true Christian may be described as one who does what is right, loves his brothers, and believes certain propositions about Jesus Christ.
A constant theme of John’s is that of abiding, or remaining. The word itself refers to constancy or permanent faithfulness. So abiding “in Christ” must be understood as abiding in the three things we have been discussing . . . righteousness, love, and truth. Put another way, you may grow but you may not evolve. You are called as Christians into a wonderful inheritance, and in that inheritance you are told to stay put.
This “remaining” brings confidence with it. We are to live in such a way that when Christ comes we might be confident (v. 28). Those who are destined to righteousness (i.e. to be like Him), and who are aware of it , prepare themselves on the journey for their arrival at the end of the journey. Those born to righteousness (v. 29) do righteousness. But there is also continuity between the birth on the one hand and the perfection and maturity on the other when Christ comes again (v. 2). Those who think this way purify themselves (v. 3).
Think for a moment how the Father must love us (v. 1). The word for “what manner” is potapen. It means “of what country?” John is so overwhelmed by the love of the Father, he asks what land it is from. Who imported this? The love of the Father is exotic.
As we have seen, John loves to cycle through his arguments for emphasis, and he does so again here. First he states his theme, then he says why Christ came, and then he tells us what it means. He does this twice. The theme the first time through is that the nature of sin is its lawlessness (v. 4). Christ came in order take that lawless sin away; in Him there is no sin (v. 5). What does this mean? Abiding in Christ, i.e. in the One who came to take away sin, is inconsistent with abiding in (remaining in) sin. No lie; righteousness is as righteousness does (vv. 6-7).
Then John does this again. What is the theme? The nature of sin is its diabolical origin (v. 8a). Why did Christ come? Christ came in order to destroy the works of the devil (v. 8b). And last, abiding in Christ necessitates a family resemblance to Him, and equally requires that we not resemble the one He came to destroy. In this antithetical context, we who are born of God do not sin. God’s seed is in us (vv. 9-10).
And so we see the contrast between the way of Cain and the way of Christ. John contrasts how Cain murdered his brother, and how Christ laid down His life for His brothers. We have come again to the second test, that of brotherly love (v. 11).
We are not to be like Cain—John makes plain that the devil was the motivation behind the murder of Abel. Cain, he says, was from (the word is ek) the evil one. In passing, we may note that this means the devil was there. This murder revealed the antithesis. Why did Cain commit the murder? Because he was evil, and his brother was righteous, and necessary antipathy must always exist between the two (vv. 12-13). There is no way it can ever be papered over. Because of this antithesis, we have clear assurance. John does not traffic in grays. He speaks of Christ and antiChrist, love and hate, righteousness and unrighteousness (vv. 14-15). He is not the apostle of splitting the difference.
John does not leave us without an exemplar of love. Love is what Christ did (v. 16). This brings us to one of our central duties, the imitation of Christ. We are to imitate Christ . . . not the devil, and not Cain. We are to imitate Him in our manners, in the little details of life. We are not to wait until the grand moment when we might perhaps die for another. We are to love each other in the humdrum details of life (v. 17) . . . particularly in the matters of alms and help for the poor.
Of course hypocrisy is out. Talking about it is no substitute, and listening gladly to a sermon in which the right behavior is praised is no substitute either (v. 18). Righteousness does. Love does.