Summa.
Children of God
1See how much the Father has loved us! His love is so great that we are called God's children—and so, in fact, we are. This is why the world does not know us: it has not known God.
2My dear friends, we are now God's children, but it is not yet clear what we shall become. But we know that when Christ appears, we shall be like him, because we shall see him as he really is.
3Everyone who has this hope in Christ keeps himself pure, just as Christ is pure.
4Whoever sins is guilty of breaking God's law, because sin is a breaking of the law.
5You know that Christ appeared in order to take away sins, and that there is no sin in him.
6So everyone who lives in union with Christ does not continue to sin; but whoever continues to sin has never seen him or known him.
7Let no one deceive you, my children! Whoever does what is right is righteous, just as Christ is righteous.
8Whoever continues to sin belongs to the Devil, because the Devil has sinned from the very beginning. The Son of God appeared for this very reason, to destroy what the Devil had done.
9Those who are children of God do not continue to sin, for God's very nature is in them; and because God is their Father, they cannot continue to sin.
10Here is the clear difference between God's children and the Devil's children: those who do not do what is right or do not love others are not God's children.
Love One Another
11The message you heard from the very beginning is this: we must love one another.
12We must not be like Cain; he belonged to the Evil One and murdered his own brother Abel. Why did Cain murder him? Because the things he himself did were wrong, and the things his brother did were right.
13So do not be surprised, my friends, if the people of the world hate you.
14We know that we have left death and come over into life; we know it because we love others. Those who do not love are still under the power of death.
15Those who hate others are murderers, and you know that murderers do not have eternal life in them.
16This is how we know what love is: Christ gave his life for us. We too, then, ought to give our lives for others!
17If we are rich and see others in need, yet close our hearts against them, how can we claim that we love God?
18My children, our love should not be just words and talk; it must be true love, which shows itself in action.
Courage before God
19This, then, is how we will know that we belong to the truth; this is how we will be confident in God's presence.
20If our conscience condemns us, we know that God is greater than our conscience and that he knows everything.
21And so, my dear friends, if our conscience does not condemn us, we have courage in God's presence.
22We receive from him whatever we ask, because we obey his commands and do what pleases him.
23What he commands is that we believe in his Son Jesus Christ and love one another, just as Christ commanded us.
24Those who obey God's commands live in union with God and God lives in union with them. And because of the Spirit that God has given us we know that God lives in union with us.